VHF Frequency Meter to cover HF bands? - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: January 04, 2020, 12:15:27 pm
content: I have this vintage Frequency Meter which covers 100 - 160Mhz.It absorbs RF of that range of frequency, then when dial is tuned for the RF, the analogue meter inflates.The tuned dial at the max.of the inflated analogue meter indicates the resonant frequency. In a way it is very similar to GDO meter.From the circuit diagram, it has two coils L1 L2 , and then variable cap, and another capacitor to the meter. Very simple construction. In test with the VHF RF, it works OK.I am wondering what would be best way to convert or add something to make it cover HF 1.8Mhz - 30Mhz range.

author: vinlove
author_rank: Frequent Contributor
timestamp: January 04, 2020, 12:26:12 pm
content: Here is the circuit diagram of the VHF Freq. Meter.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 04, 2020, 02:44:25 pm
content: It is an "Absorption Frequency Meter", or as it is more commonly referred to, an"Absorption Wavemeter".You can change the range of frequencies it functions over by changing the values of L1, L2, & possibly C1. (If C1 is a very low capacitance, it might not be suitable for lower frequencies.)http://www.clovellydonkeys.co.uk/kengreen_website/pt6_measurements.htm

author: vinlove
author_rank: Frequent Contributor
timestamp: January 04, 2020, 04:30:34 pm
content: Any commercial transverter / converter, which can be plugged into the input of the frequency meter, and expand / change the coverage of the frequency it can handle?

author: vk6zgo
author_rank: Super Contributor
timestamp: January 05, 2020, 03:16:21 am
content: Quote from: vinlove on January 04, 2020, 04:30:34 pmDoubtful, as mixing a HF signal up to VHF may have problems, due to the limited selectivity of the device.A simple mixer will probably still have some of the VHF local oscillator present, so you may peak on that.Also, if you are translating a frequency like 6MHz, using, say, a 100MHz L.O., it will appear at both 94MHz & 106 MHZ.

author: bob91343
author_rank: Super Contributor
timestamp: January 05, 2020, 06:09:57 am
content: I have just what you need. It's a Triplett 3256 wavemeter that has a frequency range from 3.5 to 30 MHz and includes a meter, I think 1 mA.Google it and you will see how simple such a device is.https://www.ebay.com/c/1500142288

author: vinlove
author_rank: Frequent Contributor
timestamp: January 05, 2020, 12:41:01 pm
content: Quote from: bob91343 on January 05, 2020, 06:09:57 amThats very similar to what I have, apart from yours covers the HF band, and mine covers VHF.Mine also has the coils inside the casing, and as permanent fixture, but yours is on outside, and is removable.I am not sure how that one coil covers 3.5 to 30 Mhz, because my other GDO Meter, Heathkit GD-1U comes with 4 different coils for each segment of the HF bands.

author: vinlove
author_rank: Frequent Contributor
timestamp: January 05, 2020, 12:44:06 pm
content: Quote from: bob91343 on January 05, 2020, 06:09:57 amI better then just keep it as a VHF Meter, because it is a vintage, and I want to keep it as original. It works great on VHF.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 05, 2020, 01:32:40 pm
content: Quote from: vinlove on January 05, 2020, 12:41:01 pmIt doesn't, there are 2 scales for the tuning so at least 2 coils are needed.

author: bob91343
author_rank: Super Contributor
timestamp: January 07, 2020, 06:59:59 am
content: It covers 3.5 to 30 MHz with one coil. There is a tap on the coil that is switched by a toggle switch.The coil is removable and plugs in with an old fashioned 4-pin tube base such as the type 80 tube uses. Why they made it removable I have no idea, because as far as I know they didn't make any other coils for it.It works as new, but isn't something I find useful.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 07, 2020, 08:04:19 am
content: Quote from: bob91343 on January 07, 2020, 06:59:59 amI should have said "or a switchable coil" but couldn't find the switch. I stand corrected.