SSB converter for AM SW Radio? - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: August 12, 2019, 09:45:00 am
content: I have a SW Radio, but it is only in AM mode. I would like to listen to Ham SSB and CW on HF bands using the radio.Would it be possible and easy to make a SSB and CW converter / transverter for the AM only Radio? Something like BFO kit? If possible where would it be connected to in the radio?Or if it were impossible or difficult to make, then is there any commercial kits for that available?Thanks

author: CJay
author_rank: Super Contributor
timestamp: August 12, 2019, 11:38:58 am
content: Yes, you need a BFO, you'd usually connect it at the 455KHz IF filter but it's impossible to say if that's possible with your radio as we don't know what it is, even if you do tell us then we may still not be able to say unless the schematic or at least the block diagram is out there somewhere.

author: vinlove
author_rank: Frequent Contributor
timestamp: August 12, 2019, 12:14:31 pm
content: My SW Am Radio is one from Amazon, RADIWOW R-108. It is super mini portable radio, extremely sensitive and has excellent audio.It doesn't come with block diagram or circuit diagram. I don't think any of the new radios you buy is supplied with the circuit or block diagram.Maybe I should look for another AM set for the project? I have another radio that does ssb and cw, but wanted to see how practical and simple it would be to make such bfo kit for this radio. Now I know it is not something that plugs into the ear phone jack or antenna terminal, but inside the radio at 455Khz IF filter. Thanks for the info.

author: borjam
author_rank: Unknown
timestamp: August 12, 2019, 12:30:32 pm
content: With some old radios I remember it was enough to put a cheap MW radio close to them. The local oscillator would interfere with the IF, effectively injecting a carrier

author: bd139
author_rank: Super Contributor
timestamp: August 12, 2019, 01:34:59 pm
content: From some googling looks like a Himark single chip radio. digital IF. Forget it. Probably won't do SSB and you're unlikely to be able to bodge it to do it. No IF strip, no BFO either.Edit: actually forget that. Found a picture of the guts:http://www.radioscanner.ru/uploader/2019/r-108_insides1.jpgLooks like there's an IFT and a separate amp in there. You'd have to trace it.

author: vinlove
author_rank: Frequent Contributor
timestamp: August 12, 2019, 05:12:07 pm
content: Yeah, maybe I have to find an old SW AM radio to do that?This new breed of chip radios are maybe like a blackbox with no much info for mod?Having said that, this RADIWOW R-108 is excellent on its own for FM, AM and AIR.Especially on FM, it receives the RADIO 4 without even telescopic antenna pulled out.My other radios struggle to receive it with their built in antenna stretched out.SW AM SWLing is also excellent. So I thought it would do great on SSB and CW if converted or with some sort of transverter BFO kit.

author: bd139
author_rank: Super Contributor
timestamp: August 12, 2019, 05:40:22 pm
content: Older AM radio is probably a better bet. They're not great for amateur radio stuff though as the main VFO is usually too drifty to be able to resolve SSB or CW properly and the IF bandwidth is very wide.Couldn't find any data on the chip in that radio at all unfortunatelyPlenty of old "communication receivers" on ebay though usually.

author: hfleming
author_rank: Regular Contributor
timestamp: August 12, 2019, 06:55:12 pm
content: Many years ago, when I was still in school, I used to listen to SSB on my parents Hi-Fi receiver with SW bands. All you need is a oscillator that you can pull a few kHz running at the IF-frequency (typically 455kHz) next to the radio. Even without a short antenna, it was good enough to listen to SSB on 40 & 80m

author: vinlove
author_rank: Frequent Contributor
timestamp: August 12, 2019, 07:47:24 pm
content: Quote from: hfleming on August 12, 2019, 06:55:12 pmAny youtube videos on this? Interesting stuff.

author: bd139
author_rank: Super Contributor
timestamp: August 12, 2019, 07:50:13 pm
content: Yes. This is one of my favourite channels. Starts with crystal set, adds BFO and uses it to receive CW:Note it's a "homodyne" direct conversion receiver. There is no 2nd IF so the BFO works at the receive frequency. That section starts at 26:00 but the whole video is worth watching.

author: vinlove
author_rank: Frequent Contributor
timestamp: August 12, 2019, 10:29:24 pm
content: Wow, fascinating video. Ended up watching the whole lot, and learned a lot. Thanks.They all look like simple radios, but sounding awesome.My MFJ 8100 Regen sounds just like the regen radio in the vid.

author: bd139
author_rank: Super Contributor
timestamp: August 12, 2019, 10:52:35 pm
content: Yeah it’s amazing the performance you can get out of something dead simple.Cool with the MFJ. I need to build a regen. Unique experience. I operated someone else’s but not built one yet.

author: johnwa
author_rank: Frequent Contributor
timestamp: August 14, 2019, 10:37:23 am
content: Quote from: bd139 on August 12, 2019, 01:34:59 pmEven if the IF is inaccessible for whatever reason, you can still inject a beat signal at the original transmit frequency:http://home.alphalink.com.au/~parkerp/projects/projbfo.htmOf course, when you retune the radio, you have to retune the BFO too...I built one of these ages ago (on a solderless breadboard, despite suggestions that they are no good for RF work), and used it in conjunction with a ghetto blaster with a shortwave band (!) to listen to SSB transmissions on 80M

author: CJay
author_rank: Super Contributor
timestamp: August 14, 2019, 12:06:28 pm
content: Quote from: johnwa on August 14, 2019, 10:37:23 amBeat me to that one, yes, you can inject a signal that way too but you need to be careful about power output for varous reasons.Breadboards aren't great for RF but can be used if you know how they affect the circuit, plus, 80M isn't particularly high frequency and should be 'do-able' easily on a breadboard.

author: bd139
author_rank: Super Contributor
timestamp: August 14, 2019, 12:09:34 pm
content: When you get to that stage you might as well stick a mixer and amplifier on your VFO and build a direct conversion receiver

author: johnwa
author_rank: Frequent Contributor
timestamp: August 15, 2019, 08:01:51 am
content: Quote from: bd139 on August 14, 2019, 12:09:34 pmYes, that is in fact exactly what i did. Then I added an RF PA and some switching, and ended up with a DSB transceiver. And then, another oscillator, and an IF strip, and I had an SSB superhet, though I never really got it working well enough to get much use out of it...

author: vinlove
author_rank: Frequent Contributor
timestamp: August 15, 2019, 08:36:19 am
content: In that case, could I use my GDO meter to inject RF to the ham band freq into the AM receiver, and get SSB signals decoded?Would it work any other freq. than 80m band such as 40 and 20m freqs?

author: bd139
author_rank: Super Contributor
timestamp: August 15, 2019, 09:05:28 am
content: A GDO would work. Might be a bit touchy though.

author: vinlove
author_rank: Frequent Contributor
timestamp: August 16, 2019, 06:45:08 am
content: I tried it with GDO, and RADIWOW R-108 on 3.5Mhz, and it worked. I was able to read CW very well.As you said, it was very very touchy. Not sure if it is a practical way for receiving SSB and CW on AM though.

author: bd139
author_rank: Super Contributor
timestamp: August 16, 2019, 08:48:18 am
content: Yeah definitely not practical for sure. Good that it worked however.Probably easier to tune lower bands as the GDOs tend to have a lower frequency span on lower frequencies so easier to get precise tuning.

author: vinlove
author_rank: Frequent Contributor
timestamp: August 17, 2019, 12:41:59 pm
content: Another video on youtube for using sg decoding SSB from AM radio.

author: tkamiya
author_rank: Super Contributor
timestamp: August 21, 2019, 06:42:09 pm
content: The concept is, SSB signal is an AM signal with carrier removed. One of the side band is also removed as it is a duplicate of the other.So all you have to do is add back that carrier, like you did with your GDO. You can do it at the frequency or at I/F. Most practical way to do it would be at I/F. You simply need a signal generator of a sort 455KHz +/- 1.5KHz with an ability to move around few 100Hz.If you are looking for the biggest bang for your buck, SDR of any kind would be good. (with a converter for HF). If this is just for fun, you could build a more stable signal generator with fine tune capability.Brings back my old days... Tweaking a dial just right to get decent demodulation. Then it would drift all over the place in few minutes.

author: 14E130
author_rank: Newbie
timestamp: January 12, 2020, 05:56:09 pm
content: Salut a tousVoila un schéma de BFO

author: bob91343
author_rank: Super Contributor
timestamp: January 12, 2020, 06:23:46 pm
content: This is just a Hartley oscillator with varicap frequency control at 455 kHz with a buffer amplifier. It's very suitable but you will have to adjust injection level as well as suffer with its frequency instability. Better perhaps to use a crystal oscillator at 455 and use the main tuning of the radio to adjust.

author: 14E130
author_rank: Newbie
timestamp: January 13, 2020, 08:33:12 am
content: Voila un autre schéma