Causes for  Power Supply Output Voltage Drop - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: September 24, 2019, 01:55:21 pm
content: What causes power supply output voltage drop? The power supply is about 20 years old it looks, and it is 13.5V output and rated for 20A continuous and 25A maximum peak.It is fine when connected to hf transceiver and in receiving. But when the transceiver is transmitting about 50 w pep. about half of its full power, the power supply drops output voltage from 13.4V to 13V, then 12.8, and then 12.5V. This voltage drop causes the transceiver blink the lights in freq window and s meter, making thump noise from the loud speaker, and transmitted audio doesn't seem contain audio at all, because the other stations can't hear and don't respond.On full 100W, the output drops to 6 - 8V at lowest coming back up to 12- 13V continuously cycling, so the transceiver dimming and blinking gets worse, and the thumping noise gets real loud, as if it will explode, and the transceiver goes dead momentarily, and comes back. No transmission takes place.The output voltage from the power supply has been monitored by DMM.Any ideas?

author: tunk
author_rank: Super Contributor
timestamp: September 24, 2019, 02:12:12 pm
content: If it uses a transformer then the smoothing capacitor may be dying.If you have an oscilloscope you could check the output.

author: radiolistener
author_rank: Super Contributor
timestamp: September 24, 2019, 06:00:25 pm
content: Quote from: vinlove on September 24, 2019, 01:55:21 pmThese symptoms looks like your antenna is broken or there is a bad connection with antenna. It leads to high VSWR and you can damage your transceiver output if you continue transmit into broken antenna.So, the first step is to check your antenna, check connectors and antenna cable. Wipe the contacts on the antenna connectors with ethanol (alcohol).Reduce transmitter power to 5-10 W and measure VSWR in the antenna cable. If it is more than 1.5, then your antenna is broken and you're needs to fix it.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 24, 2019, 06:27:44 pm
content: Bad filter caps are a real possibility. This would lead to ripple to come through to the output. For a test I would prefer a more resistive load to exclude effects of the load (e.g. like the broken antenna or a broken power amplifier).Another, less likely cause could be loose wire or cold solder joint at the rectifier so that one one half wave is used. This tends to cause audible noise from the transformer under load.

author: ejeffrey
author_rank: Super Contributor
timestamp: September 24, 2019, 06:30:27 pm
content: Quote from: vinlove on September 24, 2019, 01:55:21 pmThis is usually a hint to stop what you are doing and check your assumptions, ideally before it gets to the point "as if it will explode". You easily could have broken something already by overdriving /overloading, don't make it worse.Anyway, divide an conquer. Do what radiolistener said to check your antenna. Use whatever tools you have to test your transmitter independently. Test the power supply with a dummy load.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 24, 2019, 10:25:06 pm
content: I have 2x other power supplies of 25A rating, and when they are connected to the rig, everything is working fine.But there is a mystery.When this problematic old psu is powering hf rig and key down to a dummyload and meter, then it is fine.It is only when the antenna is connected to the rig and transmitting, the PSU drops the voltage, and create mayhem to the rig.The antenna is just outdoor end fed antenna with counter poise, and tuned to 1:1.2 SWR.As I said, when I connect other 25A power supply (more modern ones SEC1223), the rig is fine working well.What is going on here with the old psu dropping the voltage only when transmitting to the antenna, but seems ok when transmitting to dummyload full 100W?

author: vinlove
author_rank: Frequent Contributor
timestamp: September 24, 2019, 10:28:09 pm
content: If my antenna is broken, how the other power supplies work fine making good contacts on 20m SSB with 100W pep using exactly the same antenna and same power and on the same frequency? And there is absolutely no symptom of blinking displays, no dimming S meter, no thumping noise, and they don't drop output voltages at all when transmitting. Yes, they do drop, but maybe 0.01 - 0.02V max. Not blooming 1-2V at 50W pep, and definitely not 4-5V drop at 100W pep.Why when this old psu is connected to the rig, the rig goes blinking and get dimmed making thumping noise through the speaker? Also the output voltage drops to worst 6-8v and 11-12v from 13.5V when transmitting, making the rig goes dead momentarily?

author: vk6zgo
author_rank: Super Contributor
timestamp: September 25, 2019, 12:46:24 am
content: It does sound a bit as if RF is getting into the PSU's control circuitry.What you need to test this is a similar DC load which doesn't produce RF.You can probably pick up some old style sealed beam headlights from an auto wrecker.These are normally rated at about 55 Watts for the high beam, so if you get two, that gives you a pretty good workout for your supply!If the PSU stays up OK, you have a problem with RF sensitivity, if not, you just have an old fashioned power supply fault!

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 06:12:01 am
content: Yes, that sounds right.I have never known that power supplies could be also affected by RF. But it does, and some PSU seem suffer from the RF more badly than others.Whether it is by age or design of the psu or the quality parts I am not sure. But when it does get RF affected, it makes the PSU useless for powering TX rigs.I feel that there is no way that your shack could be 100% RF free when you are transmitting using your rig and antenna no matter how good your ground system could be. I have a field strength meter in the shack, and always it detects RF from the coax, mic lead and ATU and also back of the rig and also power lead from the rig to power supply. And my the other 2x power supplies are all OK, they just keep working fine in the same RF level that malfunctions the old power supply.The only way to have no RF problem is to go QRP less than 5 Watts or maybe 10Watts Max. But then for that kind of power, I don't need heavy and expensive 25A rated psu. A 5A rated psu will do.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 11:38:35 am
content: Quote from: vinlove on September 24, 2019, 10:28:09 pmit seems that your antenna is broken and has high VSWR. It leads to return back RF energy. This returned RF energy may disrupt normal work of electronic devices (such as power supply, measurement devices and other) if it is sensitive to RF power.Your second PSU may be more protected for RF leakage.Try to check power supply ground and antenna cable outer braid with neon lamp. Does it have light during transmission?The second possible root of cause is that your problematic PSU has dead capacitors. But the first root of cause with broken antenna looks most likely for your symptoms

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 11:52:10 am
content: Quote from: radiolistener on September 25, 2019, 11:38:35 amContacted many stations using the antenna on 20M last night, and 40M this morning and 80M this afternoon.How can a broken antenna make you contact other stations? I was running 100W full power of the rig.How can a broken antenna do that?If my rig is powered by my original SEC1223, it is working fine.But when the problematic old power supply is connected, and powers the rig, it makes the rig go dead when just pressing the microphone push button.Strangely, if it is connected to a dummyload instead of the antenna, then it is OK.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 01:05:38 pm
content: Quote from: vinlove on September 25, 2019, 11:52:10 amAny piece of wire can work like antenna, you can make contacts with many stations even with household nail as antenna.But efficiency depends on how good your antenna is matched with cable and how good is antenna efficiency.Bad antenna (such as household nail) has bad efficiency and it is diffucult to match it with the cable.When you use bad antenna, your transmitter needs to use much more power to compensate bad efficiency. Unused RF energy will be returned back and leads to heating output amplifier. Also returned back RF energy leads to interference for electronics, include power supply regulator.So, you can still use broken antenna to make QSO and have many contacts on 20M, on 40M, on 80M or any other band. But it is not good for your transceiver. Broken antenna returns back a lot of RF energy and it may damage your transmitter output. Also it may leads to high power RF leak, which may affect function of nearby electronics (include PSU) which is sensitive to high power RF emission.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 01:10:45 pm
content: Quote from: radiolistener on September 25, 2019, 01:05:38 pmMy antenna is not bad or broken. It is a 40 meter long End Fed Wire with counter poise. It is 3:1 SWR without ATU.It is not easy to contact with someone 1000 miles away with even large commercial antennas due poor band condition, so that some people are using amps and run 400 - 700Watts.Saying the you can contact someone with a piece of string or piece of nail on HF as antenna, sounds too extreme. Yes, you can contact someone in your house maybe, and when in sunspot maximum time, but not these bad band condition time, and not someone 1000s miles away.I can see your point RF coming back and disrupt the PSU, in some respect, but it doesn't convince me because my other power supply works perfect with the rig and antenna.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 01:16:11 pm
content: Quote from: vinlove on September 25, 2019, 11:52:10 amThere is nothing strange. This is typical and expected behavior for broken antenna.As I mentioned above, SEC1223 may be more protected from RF emission, so it works more stable with high power RF leakage. The second PSU may be more sensitive for high power RF leakage and it leads to unstable work.In any case there is strong indication that your antenna may be broken and you're needs to check it. If your antenna allows to make QSO it doesn't means that it is not broken. You're needs to connect SWR meter between your transmitter and antenna to measure VSWR.Also check your antenna cable, PSU cover and transmitter cover with neon lamp. Neon lamp is simple and cheap way to check if there is high power RF leakage.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 01:22:37 pm
content: Quote from: vinlove on September 25, 2019, 01:10:45 pmyou can use piece of nail to make contact 1000s miles away, the question is how many kiloWatt energy you will waste to transmit the same amount of energy as with good antennaAgain, if your antenna allows to make QSO, it doesn't means that your antenna is not broken.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 01:33:07 pm
content: Quote from: vinlove on September 25, 2019, 01:10:45 pmVSWR=3 is a lot. Normal antenna should have VSWR smaller than 1.5. Values up to 2.6 in some case can be accepted for wide bandwidth, but with some assumptions. But VSWR=3 is not acceptable.Check your antenna, may be there is burned out or just oxidized contact with counter poise. May be there is some short circuit or broken cable (for example crushed or worn by wind and bad weather).

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 01:41:35 pm
content: Quote from: radiolistener on September 25, 2019, 01:22:37 pmMy HF transceiver stops transmitting if SWR is higher than 3:1. No output, so it cannot damage the P.A.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 01:45:19 pm
content: Quote from: vinlove on September 25, 2019, 01:41:35 pmHigh VSWR protection not always work. So it doesn't guarantee that your PA will not be burn out with broken antenna. Especially if you work at maximum power.You're said that your antenna has VSWR=3. It means that it returns back RF energy. This energy come to your radio shack and may make random RF emission leakage. So it affects your power supply. This influence may be decreased or increased just by a small location change of PSU, TRX, ATU or coax cable. It's just random, so you cannot expect stable condition with high power RF emission in your radio shack.Just fix your antenna. It should give you VSWR 1.5 or smaller with no ATU and these symptoms will disappears.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 01:50:25 pm
content: Quote from: radiolistener on September 25, 2019, 01:45:19 pmIt is working great. It is an old rig about 40 years old, and it is still working like new. I have had it for about 20 years. No problems at all.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 25, 2019, 01:51:50 pm
content: Your antenna does not have to be actually "broken".End fed antennas with a counterpoise are pretty notorious for causing "RF in the shack".Obviously, there are "workarounds" but as I have had very little experience with such antennas, I'm not sure what would work.The only times I have had RF in the shack were:-(1) I was operating an old tube taxi radio on 2m with just a piece of brazing rod stuck in the SO239 socket---- I got "tingles" from the metal grille on the microphone.(2) Playing around with my HF rig, trying to use a 20m dipole on 40m.Using an ATU, I actually got a fair match, but the radiating bit of the antenna system was pretty much the coax feeder.The first time I keyed it up, I could smell ozone a bit, but not feel anything.The second time, the RCD on one end of my power extension cord dropped out.From these incidents,I learnt:-(1) Don't put your nose too close to a metal grille on a mic if you are running "silly" antennas.(2) RF will trip a RCD.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 02:01:00 pm
content: Quote from: vinlove on September 25, 2019, 01:50:25 pmIt may work well with some conditions, but when you have RF leakage in your radio shack it just random case. You can just move your cable for a little and it will burn out your rig or some other electronic equipment nearby. Antenna tuner placed in the radio shack cannot remove RF leakage. For example, it can bypass it through antenna tuner metal case.You can reduce it by using good RF choke on the coax cable before coax cable entering into your radio shack. Also place the second RF choke near antenna feed point, it will also reduce noise level.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 02:07:08 pm
content: I am monitoring RF in the shack with field strength meter, and it is always there. But at one time it was really bad, and it was when I was using indoor wire antenna.The FS Meter went crazy, and people told me I have a bad audio or distortion on my audio. A lot of them didn't even answer to my calls.SO I put End Fed Wire with counter poise out in the garden, and it is a lot better. I can make contacts with good audio reports and good sig reports too.But RF is sensed by the FS meter always, but it is a lot less than the indoor wire antenna times.But no matter what happened in the past, there has never been a problem with Power Supply Voltage Drop.When I got the old power supply, it started killing the rig when TXing, and voltage drop was just unacceptable.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 02:26:58 pm
content: Quote from: vinlove on September 25, 2019, 02:07:08 pmUsually antenna contacts or cable will be worse after some time (wind, rain, snow, damp will make oxide rust and rot). It may leads to much worse VSWR. For example, if your new antenna has VSWR=3, now it may become VSWR=5 or even 10. So, now much more RF power is returned back into your shack and make more higher RF emission around your rig. It may leads to violation of the functions of electronics nearby you rig. Include your PSU.It may also damage your transmitter, even if it has high VSWR protection. So, even if your SEC1223 is more protected from RF leakage, it doesn't means that all is okay.After some time you may found burned out transceiver, PA or other equipment and it should not be surprise for you, because you already have signs that something is wrong with your antenna.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 03:33:37 pm
content: Quote from: radiolistener on September 25, 2019, 02:26:58 pmI have been a Ham Radio operator for 25 years, but that sounds too pessimistic and negativeI can easily break the antenna somewhere, and try to tune with ATU, and the ATU will just keep sitting at the infinite SWR until the breakage is corrected.If ATU doesn't know what is broken antenna and what is a good antenna to tune, then it would be useless, and no one would buy them. But they are very accurate and it knows what is broken antenna and what is reasonably good antenna to tune. So it is a must have.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 03:59:16 pm
content: Quote from: vinlove on September 25, 2019, 03:33:37 pmThen you should know what is coax feed line common mode choke, and why ATU cannot eliminate RF leaks which can easily bypass your ATU through metal case and outer side of coax cable braid.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 04:10:38 pm
content: Quote from: vinlove on September 25, 2019, 03:33:37 pmATU cannot help in your case. It cannot eliminate RF emission from common mode current on the antenna cable, which is already present in your radio shack. There is no way to eliminate it with any kind of device placed in your radio shack. Since it is already here, you cannot get rid of it.You're needs to take care about common mode currents outside your radio shack, before these RF currents gets into your radio shack. If it is already here, there is almost no way to eliminate it.Just read some basics about it. For example here:http://www.k0bg.com/common.html

author: OwO
author_rank: Super Contributor
timestamp: September 25, 2019, 05:13:36 pm
content: I've seen this problem before. I had a 30V 10A power supply that decreased its voltage when there was conducted RFI from the antenna, and another 5V wall wart that increased its voltage. The EMI is rectified by diode junctions in the power supply feedback circuitry and causes a DC bias. You should feel lucky that your power supply decreases its output voltage rather than increase it. A temporary solution is to add ferrite clamps to the antenna feed line (you will need many of them!) and the power supply DC output cable. I would use at least 5, they are not expensive and at this power level one ferrite will easily saturate. I've had ferrite clamps on the feedline get hot after transmitting for a while. Long term solution is to redesign the antenna so that no RFI is conducted down the feedline outer shield, for example with a balanced antenna and a proper balun.EDIT: VSWR has nothing to do with this. 1:3 VSWR could be better but I wouldn't be concerned about it at all. The cause is common mode currents flowing on the outer side of the coax shield (conducted EMI).

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 05:15:35 pm
content: Quote from: radiolistener on September 25, 2019, 04:10:38 pmI never said ATU can eliminate RF.I said that ATU knows how bad your antenna is, and it matches the output of rig to the antenna.But if your antenna is broken, ATU will not match it.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 05:33:23 pm
content: Quote from: vinlove on September 25, 2019, 05:15:35 pmThat is wrong. ATU doesn't know about antenna anything. It just match TRX connector impedance with ANT connector impedance. It even don't know if there is exist antenna or not. You can disconnect your antenna and good ATU will consume all energy from TRX. So, it's doesn't matter for ATU if you have good antenna or broken antenna or no antenna at all.In any case ATU cannot help with this issue, because it cannot eliminate common mode currents from broken antenna.For example, cable braid can be torn off from counter poise at antenna feeding point. It can happens due to wind and other weather effect. In such case you will get high common mode currents. ATU cannot remove it. You will be able to make QSO and your antenna will listen signals, but it is broken and works much worse than it should be. Also you will get a lot of noise from home electronics.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 06:52:38 pm
content: Well, I don't have any RF problems at all in my whole house everywhere.Everything is working 100% fine.The old power supply was only problem.Now I sent it back for full refund to the seller, I now have no problems whatsoever.I am just enjoying a lot of great contacts on HF with my antenna and HF rig powered by SEC1223 power supply.I think you are wrong. Broken antennas cannot make any contacts. ATUs don't tune up broken antennas either.I just have a good working end fed wire antenna with counter poise. I added more wire to counter poise tonight, and it even works better.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 25, 2019, 09:36:14 pm
content: I think your problem is that you have never transmitted RF in your life? From your ID, you are a RadioListener, that is SWL = Short Wave Listener right?Tuning receiving antenna and transmitting antenna is totally different. Your can tune your receiving antenna with ATU even if it is broken, and use it. But you will never be able to tune broken antenna for transmitting RF. It just simply won't happen.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 10:12:11 pm
content: Quote from: vinlove on September 25, 2019, 06:52:38 pmYou're wrong again. Some time ago I made QSO on 10m band by using a piece of heating water pipe inside house instead of antenna. It works not so good as normal antenna, but still works and you can use it to make contacts. Especially if your friend on the other side using very good antennaYou can use broken antenna and any piece of metal for QSO on short wave. But it's efficiency and noise performance will terrible in comparison with good antenna of course.Normal antenna doesn't have VSWR=3. It should be properly matched with the cable. So it will have VSWR about 1.0.And good antenna doesn't needs ATU on transceiver side. Because good antenna always use impedance match circuit at the feeding point to prevent energy loss in the cable.

author: radiolistener
author_rank: Super Contributor
timestamp: September 25, 2019, 10:16:03 pm
content: Quote from: vinlove on September 25, 2019, 09:36:14 pmAgain wrong, I have license and call sign. I like to listen the radio, this is why my nick is radiolistener, but it doesn't means that I'm not using TX.The problem here is that you don't understand what is common mode currents and why it cannot be removed by your ATU. Basically it means that you're don't understand how antenna works and how to properly feed it.That's strange, I thought any radio amateur who working with transmitters should know about common mode currents and how to fix it.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 26, 2019, 12:15:20 am
content: Quote from: radiolistener on September 25, 2019, 10:12:11 pmNot really, many people use open wire feeder to tune a "doublet" antenna, which is used as an "all band antenna".This is cut to roughly a half wavelength long at the lowest frequency required.They use an ATU at the transceiver end of the feeder, because tne antenna feedpoint impedance varies widely over the complete range of frequencies they use.Open wire feeders have very low losses & can be operated at high VSWR figures which would cause very high losses using normal flexible coaxial cable.This has nothing to do with "RF in the shack"-----even matched dipole antennas using coax can exhibit this problem, due to the lack of a balun to convert between the balanced antenna & the unbalanced feeder.At lowish power levels, like 100Watts & at lower frequencies, this is minimal & is often ignoredWhen using a dipole at lower than its designed frequency, as in my quoted case above, the antenna & feeder tend to look like a "top loaded" end fed antenna, hence the coax becomes "hot" with RF.In the OP's case, there is no feeder, the antenna wire just extends into the shack.The other terminal of the ATU is connected to the "counterpoise".There is, hence, nowhere to put ferrite on the feedline .The logical places for ferrite beads, clamps or whatever, are on the AC Mains input to the PSU & its DC output.With all due respect to this eminent forum, I would suggest this discussion would be better taken over to QRZ.com.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 26, 2019, 06:53:53 am
content: A very similar case of thread is running in eham.com, and everyone has been agreeing on the fault with the power supply, and talking about rebuilding it.https://www.eham.net/ehamforum/smf/index.php/topic,126714.0.html

author: vinlove
author_rank: Frequent Contributor
timestamp: September 26, 2019, 07:40:43 am
content: Not a single person is suggesting broken antenna for the voltage drop of the old power supply problem?

author: OwO
author_rank: Super Contributor
timestamp: September 26, 2019, 09:47:49 am
content: The PSU may be overly susceptible to conducted EMI, but having conducted EMI in the first place is pretty bad. You don't know what equipment in your house will malfunction, and the amount of EMI conducted from a monopole antenna fed 50W is probably many orders of magnitude above what FCC requires for EMI immunity. Again I think the best solution is to not use an unbalanced antenna at this power level. Just because the antenna transmits fine doesn't mean you don't have a problem. A simple dipole with a proper balun would be better. A easy way to test is to build a diode rf probe (diode + capacitor + led), and touch the probe to the coax outer shield conductor while holding the ground of the probe with your hand. If the LED lights then you have too much conducted EMI.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 26, 2019, 10:39:47 am
content: I have another old PSU, and it doesn't have RFI problem when powering on the HF rig, and using the same antenna and same power, and it runs fine.So 2x PSU (one modern and one very old) PSUs working fine, but that susceptible one was making serious problem.If you have RFi problem, you will know immediately.

author: radiolistener
author_rank: Super Contributor
timestamp: September 26, 2019, 12:08:28 pm
content: Quote from: OwO on September 26, 2019, 09:47:49 amcompletely agree. Also working in extreme high electric and magnetic field strength (which is the case when you're sitting very close to the radiating cable with 100W transmitter) is not good for health.This is why proper balanced antenna with RF choke is more safe in transmit mode and has much less noise in receive mode.

author: radiolistener
author_rank: Super Contributor
timestamp: September 26, 2019, 03:08:49 pm
content: Quote from: vinlove on September 25, 2019, 06:52:38 pmAccording to your description, there is clear indication that you have issue with antenna.Look here:Quote from: vinlove on September 24, 2019, 10:25:06 pmThis is pretty clear indication that something is wrong with your antenna.Such issue is expected with broken antenna which leads to common mode currents and high RF interference. RF interference affect electronics, in your case it affected PSU functions and it drops down the voltage. You're lucky that there was voltage drop instead of voltage increase.Your second PSU is more shielded from RFI. But it doesn't fix your broken antenna, it just hiding symptoms of the problem.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 26, 2019, 07:58:53 pm
content: Quote from: radiolistener on September 26, 2019, 03:08:49 pmI feel that you are obsessed with broken antenna for some reason, and just keep talking from one side only, while ignoring the other side. Why are you ignoring the fact that there are 2x other power supplies, which work great with no problems? Why are you ignoring the fact that there is no problem with RFI in anywhere and anything when transmitting in the shack?

author: radiolistener
author_rank: Super Contributor
timestamp: September 26, 2019, 08:10:40 pm
content: Quote from: vinlove on September 26, 2019, 07:58:53 pmbecause you're stated that "bad" PSU works ok when you use dummy load instead of antenna. But it works bad when you use real antenna. Exactly this happens when you have broken antenna and common mode currents on the feed line.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 26, 2019, 08:42:03 pm
content: Quote from: radiolistener on September 26, 2019, 08:10:40 pmThe problem was not that simple, and it is not one sided. That's why I started this thread. But just keep saying about the broken antenna is not helping anything, because the antenna is not broken. It is a classic HF antenna which has been in use for many many years.The old power supply had problems of some sort - that's what I wanted to find about. Not the antenna. If you transmit, then there always be some level of RF, but that doesn't mean that your power supply has to die, also killing the HF rig. No, it doesn't work that way.To have that kind of problem, you must be running about 1000 Watts into a severed coax cable or something.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 26, 2019, 11:50:43 pm
content: Quote from: vinlove on September 26, 2019, 06:53:53 amExcept thatALPARDstill sees the fault when transmitting into a dummy load!

author: radiolistener
author_rank: Super Contributor
timestamp: September 27, 2019, 12:06:18 am
content: Quote from: vinlove on September 26, 2019, 08:42:03 pmNo. I have the same problem with 15 Watt transmitter and broken antenna, a lot of electronics fails. Such as multimeter, some controller-driven circuits and even transceiver go crazy, blinking with random symbols performing random operation and so on.When I'm using dummy load or another good antenna all is ok. But when I'm trying to use broken antenna I get some kind of paranormal activity of almost all electronic equipmentAnd this happens with just 15 W power output...And all electronics is ok. The problem with antenna.

author: drussell
author_rank: Super Contributor
timestamp: September 27, 2019, 12:18:24 am
content: Quote from: vinlove on September 26, 2019, 10:39:47 amJust because you have other equipment where the operation isnotadversely affected by the operating conditions (in this case, stray RF,) doesnotmean that the symptoms you were seeing with the subject PSU aren't caused by those conditions.I suspect that it would have worked fine in a "cleaner" RF environment, since it worked fine into a dummy load or, alternatively, if you actually did some testing and found that you really do indeed have minimal RF in the area as you state, then there should have been some easy repair or modification to some sort of defective or missing RF filtering, bypassing, shielding or some such issue in the supply. I highly suspect the former.Furthermore, if you had at least tried poking around with a simple RF probe or trying to isolate and shield the supply to see if you could effect any change could have yielded some interesting results.I'm mostly just curious as to why you would ask for help and suggestions but then steadfastly refuse to actually investigate any of the suggested courses of action.QuoteAre yousureabout that?It would seem that is not always so.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 27, 2019, 12:27:19 am
content: 'vinlove, just test the antenna with a multimeter & another long length of wire, already!That way you can determine if you are right &radiolisteneris not.About the only things that can be "broken" with such a simple antenna are:- open circuits or high resistance connections.All of these can be easily determined with a DMM on the Ohms range.My feeling is that there is nothing wrong with your antenna, & that your problems are just due to a characteristic of such antennas.A very well written discussion on end fed antennas appears at:-https://www.w8ji.com/long_wire_antenna.htm

author: m3vuv
author_rank: Super Contributor
timestamp: September 27, 2019, 02:19:03 am
content: seems everyone is jumping on the antenna fault band waggon,i was trying to setup the bias on a new pa fitted to my ts-850,after setting the bias for the finals i proceded to set up the max power and swr protection levels,firstly trying to set the power to 100 watt into a 50 ohm dummy load i could only get 70 watts max,also noticed the psu output dropped to about 11 volts on tx,i scratched my head and shelved it for a few months,in the meantime i had 5x2n3773 transistors left over from a diy psu build,my psu was a manson ps-30m,this had 6x 2n3055 pass transistors,i decided to replace these with 8x 2n3773 transistors along with a 50 amp bridge rectifier,when i removed the old transistors i tested them,1 was oc collector to emitter,after rebuilding it,i hooked the ts-850 back up to it,keyed up and saw 170 watts into a dummy load and no volt drop from the psu!,i suggest you may have a similar issue with your psu,just my 2pence worth.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 27, 2019, 02:29:53 am
content: Quote from: m3vuv on September 27, 2019, 02:19:03 amOverkill! I like it!I remember reading an article in 73 magazine many years ago, where they had some uncomplimentary things to say about 2N3055sIn the article, they chucked them out & replaced them with 2N3773s, with much improved performance.

author: tautech
author_rank: Super Contributor
timestamp: September 27, 2019, 02:50:56 am
content: IIRC only the Motorola 3055's were worth their salt and most other brands came a distant 2nd.OTOH 2N3773 had a bigger die IIRC.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 27, 2019, 06:48:08 am
content: Quote from: drussell on September 27, 2019, 12:18:24 amThe problematic PSU was bought from online seller and it had 14 days return warranty. They put a warranty sticker seal on the casing, saying that if the seal is broken then warranty will be invalid. So I did not even try to open it up to see whats wrong with it.I didn't want the situation where, oh I will try to fix it, and open it ip, and find out something is really gone wrong, and even the parts are not available due to it being a very old PSU.So, I contacted the seller for the problem, and returned it for full refund.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 27, 2019, 06:53:09 am
content: Quote from: m3vuv on September 27, 2019, 02:19:03 amThe antenna is not broken at all. It is very thick heavy duty wire, and I checked all the continuity with the DMM.Yeah, I think your suggestion seems the answer.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 27, 2019, 07:22:57 am
content: Quote from: radiolistener on September 27, 2019, 12:06:18 amI don't know what rig your are running, but if your antenna is indeed broken, then your rig must stop transmitting from high SWR protection circuit activated.Maybe you are running an old rig with tube P.A.?And if your antenna is broken, firstly, your reception would be bad, and you cannot hear much.

author: tautech
author_rank: Super Contributor
timestamp: September 27, 2019, 07:44:18 am
content: Any antenna with a SWR of 3 I would call broken too.We should remember that an antenna can be considered a transformer in that it converts all available transmitter power into RF by transforming the 50 ohm feed into atmospheric radio waves.Why else would we have tools like VNA's ?

author: vinlove
author_rank: Frequent Contributor
timestamp: September 27, 2019, 07:53:17 am
content: Quote from: tautech on September 27, 2019, 07:44:18 amIt would be best to have antenna with SWR less than 3:1 for all bands, but in real world, it is difficult to achieve. Isn't that why we have tools like ATU or antenna matcher?

author: vinlove
author_rank: Frequent Contributor
timestamp: September 27, 2019, 07:57:04 am
content: My end fed wire is 1:3 SWR on 14.1 Mhz without ATU, straight through, by the way.1:1.5 at 14.250 Mhz.I can use it without ATU on 14Mhz SSB. The PSU was going crazy while the rig was transmitting on 14.250 Mhz.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 27, 2019, 09:33:32 am
content: On other bands it is SWR 1:4 - 1: 5, so I must use ATU on other bands. It works OK. It is not a DX antenna by any means, but it gets out, and makes contacts with most parts of Europe even in this poor HF band condition.

author: m3vuv
author_rank: Super Contributor
timestamp: September 27, 2019, 01:32:40 pm
content: with all this waffle about bad swr,why the hell dont you tear the psu apart and disconect all the pass transistors then do a diode check,put your dmm in diode test mode then stick the dmm +ve probe to the base of each transistor and firstly the black _ve probe on the collector and note the reading,then repeat and do the same on the emmiter,reading,ie foward volt drop should be about .6/.7 volts,thats assuming they are npn pass transistors,if pnp reverse the leads and repeat,maybe an idea to measure the emmiter resistors while your there,expect about .1/.3 ohms on these,gool luck m3vuv.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 27, 2019, 03:46:35 pm
content: Waffles have been caused by the Radiolistener's obsession with broken antenna, and his insistence on the point, as the sole source and main cause of the problem.And you must have written your post without reading my previous post, which I explained why I have not bothered opening it up to have a look into it.

author: m3vuv
author_rank: Super Contributor
timestamp: September 28, 2019, 12:19:11 am
content: has this gone back for a refund then?

author: vk6zgo
author_rank: Super Contributor
timestamp: September 28, 2019, 12:42:06 am
content: Quote from: tautech on September 27, 2019, 07:44:18 amHF & MF transmitting is a different world!It is often more efficient to construct an antenna which radiates well, but doesn't by itself, match any standard feeder cable impedance.It is easy, technically, to design an antenna matching unit for a fixed frequency, as would be used for a MF or HF broadcast site.(Mechanically, they are monstrous, but that is another story).Amateur Radio offers another level of complexity, as antennas are expected to operate over quite wide frequency ranges, fit into a suburban backyard, & be economical.A Broadcasting or Comms authority can quite happily scatter things like "Dual Frequency VerticalRadiators", Rhombics, Curtain Arrays & the like around a huge paddock, all with their own dedicated feeders & coupling circuits.They are huge, & cost "a King's ransom" to replace, so their lives are measured in decades."Hams" on the other hand, often "chuck up" a quick wire antenna one "Sat'day Arvo" & go on to enjoy their hobby.Of course, dipoles for each band of interest will usually offer VSWRs of better than 1.5:1, but the problem of space arises again.This is why things like End Fed random antennas, G5RVs, or open wire fed untuned doublets exist.The military have a similar problem with HF Comms in the field (Obviously at their home bases they can put up anything---- like the enormous HF Log Periodic at Swanbourne Military Barracks, or the equally large one at Pearce air base, both in West Oz).

author: radiolistener
author_rank: Super Contributor
timestamp: September 28, 2019, 02:38:05 am
content: Quote from: tautech on September 27, 2019, 07:44:18 amyeah, antenna is just impedance matching circuit between feeding line and free space, which impedance in the air is about 376.7 Ohm

author: tautech
author_rank: Super Contributor
timestamp: September 28, 2019, 03:12:15 am
content: Quote from: vk6zgo on September 28, 2019, 12:42:06 amHere's a local one not far from me and I've always marvelled at the enormous Yagi's and some of the other weird and wonderful arrays.....I have no idea what they are.Top left and bottom right the beam is clearly visible as a shadow. Zoomed in with Google maps measure tool the beam seems ~20m long.Quote from: radiolistener on September 28, 2019, 02:38:05 amThanks for that, Gurgle did me no favours trying to find the real value before I posted yesterday.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 28, 2019, 09:50:33 am
content: Yes, this problem was quite strange one.I have had very severe problem with RF feedback into t he rig due to bad antenna SWR, but usually symptoms were, poor audio report on TX, bad distortion on TX audio and hot microphone and switches and dials on the rig burning my fingers when touching.I have never seen power supply dropping output voltages and killing the rig. Fortunately I had another 2x power supplies to test, on the same freq. same power output and same antenna, and they don't have problems.Hence why I concluded the power supply is at fault. But where and why? I am still not 100% sure. All I know is it was not fit for powering HF radio transmitting. But it puzzled me still, because it looked OK when testing with a dummyload.

author: drussell
author_rank: Super Contributor
timestamp: September 28, 2019, 07:41:06 pm
content: Quote from: vinlove on September 28, 2019, 09:50:33 amYou're still puzzled because you refuse to admit that one way or another, it was caused by RF from your antenna.Now, I do agree that your antenna setup may well not be "broken" per se, as any random single wire antenna will obviously not magically produce perfect radiation out of only the part of the antenna you "want" it to radiate from, (strung up in the air somewhere, etc.)ANDthat random wire antennas are often used with great success. Nevertheless, the fact remains that the power supply in question operated satisfactorily while transmitting into a dummy load, and then went bonkers when you were actually radiating RF from your antenna, feedlines, chassis, ground wires, interconnection wires, power wires, etc. Radiators of both the intended and unintended variety.There are whole volumes devoted to the topics relating to containing and shielding RF in transmitter and antenna design but you refuse to accept the fact that just because your rig works and you are able to communicate, there must be no influence at all on the subject power supply from your rig. This is an incorrect conclusion. The evidence shows that it obviouslyWASinfluencing the power supply in some way.Now, the question as to WHY, whether it was just particularly sensitive to stray RF (and therefore unsuitable for the task at hand in the supply's current state) for some reason, or whether you have far more RF in your shack than you think, is certainly an open question.The fact that two other supplies happen to operate satisfactorily in the same RF environment does not necessarily mean there was anything "wrong" with the other supply, other than in your exact test setup it didnotwork satisfactorily and thus did not meet your requirements as implemented. Whether or not that could be corrected by something as simple as correctly grounding the chassis, or adding some kind of filtering or shielding is obviously unknown.The fact remains that the "unknown influence" on the supply in question that you seek, that which made it misbehave, was either related to the radiated RF conditions surrounding it, or your transmitter is drawing enough extra power when operating into your antenna compared to what it draws when driving the dummy load, to cause the supply to be overloaded and the output to drop out. You could have double checked that possibility by simply comparing the current drawn while operating into the dummy load vs. operating into the antenna.

author: vinlove
author_rank: Frequent Contributor
timestamp: September 28, 2019, 08:25:32 pm
content: I checked the currents, and they were the same. Nothing unusual was noted on current draw. If problem was noted, I would have mentioned here.A few year ago, I even used to use indoor dipole in the room, and never had problem like that.Your argument is similar to something like, the problem with the power supply is, because it was switched on, if it weren't switched on, it wouldn't have been problem. RF caused it? So, if power supply drops the output voltage and kills the HF Rig it was powering on, when RF is transmitted, what use is that?I am certain, I could get 100s of other power supplies, and test them one by one, and they will be all fine for transmitting in this set up, if they are normal 25A rated power supply with 13.8V output.