Info on G3WPO Transverter

Questions and answers on 4 m transceivers, transverters, antennas, etc.

Info on G3WPO Transverter

Postby G0TCD » Tue 29 Mar 2016, 14:18

Hi all.

I'm dusting off my old G3WPO designed 4m transverter, and while it works, it's bit deaf so I'd like to try and tweak up the receive side.

Unfortunately, I haven't been able to find the original construction information (which from memory was an article from the Ham RadioToday magazine), so I was wondering if anyone has a copy of the article, or a schematic for this transverter.

Thanks,
Ian, G0TCD.
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Re: Info on G3WPO Transverter

Postby GI0GDP » Tue 29 Mar 2016, 22:21

Try this

https://groups.yahoo.com/neo/groups/FOU ... les/g3wpo/

you may need to join the group if you havent already

regards
Geoff
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Re: Info on G3WPO Transverter

Postby G0TCD » Thu 31 Mar 2016, 11:09

Thank you very much for the link.

I'm still waiting for my request to join the group to be approved though. Hopefully I'll get that soon.

73,
Ian.
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Re: Info on G3WPO Transverter

Postby G4VCJ » Wed 13 Apr 2016, 15:01

I am using the same transverter and the 25w linear by g3wpo and have been doing so for years with no problem have a spectrum preamp which helps also now have mml 70 mhz 100w lin ant 3el trident
73 Bob G4VCJ/G6CGY
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Re: Info on G3WPO Transverter

Postby G4FKK » Sat 30 Apr 2016, 09:16

Hello Ian - did you get the info you were after? I have a pdf of the original articles if you're still in need. I use my version fairly regularly and it seems very sensitive.

73 Martin - G4FKK
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Re: Info on G3WPO Transverter

Postby G4IRX » Sun 21 May 2017, 14:30

I bought a 6m version of this transverter back in 2010 and the necessary components to convert to 4m. I've just realised that this design is was over 30 years old now!

I've finally completed the component changes and done most of the alignment. LO is running at 41MHz rather than 42MHz due to a crystal being readily available. RX seems to work, at least on the bench. I do however have a problem with lower than expected output. The output transistor in the original design used a BLY33 but a 2N3553 has been fitted. I'm getting a maximum output of 0.4W, I can get a bit more but that's at the top of the linear range. Also the PIN diode attenuator on the input doesn't seem to have any effect. I've checked the diodes as best I can and they seem OK.

Is the 2N3553 a suitable device or do I need to change any components? I also have a BLY34 available which appears to be the similar to the 33 (FM rather than AM service) as far as I can tell searching for data sheets on the internet.

Thanks for any helpful advice.
Nick G4IRX
Nottingham IO92JV
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Re: Info on G3WPO Transverter

Postby GI0GDP » Mon 22 May 2017, 08:55

Hi Nick,
Even 30 years ago i wouldn't have used a 2N3553 or 2N3866 (both 28v devices) in this position although it was very common to do so on the grounds of availability and cost.The device of choice would be the MRF237 TO-39 grounded emitter device. Not cheap these days on Ebay or any where else. The MOSFET you try would be a RD06 from SDR Kits. This wont be a drop in device either mechanically or electrically but is a modern device worthy of a try.
Let the group know how you get on and just be careful with bias initially with either the bi-polar or MosFet.
cheers
Geoff
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Re: Info on G3WPO Transverter

Postby G4IRX » Mon 22 May 2017, 15:19

Hi Geoff,

Thanks for the suggestions. I'd forgotten the 2N3553 was a 28v device, that probably explain the low power
I did manage to find some MRF237 equivalents, SD1127 for a reasonable price, they are also grounded-emitter, so that's one option. The circuit has bias resistors in the emitter circuit (Q4) as well as a diode to provide base bias so if I use one of those I'd probably have to modify that. I've also got this one BLY34 which appears to be a 12v device now I've managed to locate some data online.

Ideally I should be using more modern components, but keeping with the age of the design I'd prefer a bipolar over the mosfet.

wpo_transverter_tx.jpg
wpo_transverter_tx.jpg (36.62 KiB) Viewed 389 times
Nick G4IRX
Nottingham IO92JV
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Re: Info on G3WPO Transverter

Postby OH1ZAA » Tue 23 May 2017, 07:27

Hello Nick,

For my 50/70 MHz beacon experiments I ordered 2SC1971's from a couple
of sources. Out of curiosity I first purchased these from two Hong Kong
eBay shops, but both turned out to be fakes with the collector zenering at
6 - 8 volts DC. The base was a diode, but did not affect collector current.

Now I have got a pair (£5 each) from UK-based Enigma-component-shop.
At least the current gain (hFE) is about 170 times (tested with 1 mA bias).
I have not tested the RF-performance yet, but you should get at least 13 dB
gain on 70 MHz up to over 5 watts RF (slightly better than the MRF237 and
easier to mount for cooling, tab on GND).

Cheers/73, "Zaba" OH1ZAA / OF3BCX


P.S, Yesterday a nice opening on 70 MHz with 13 DL, some G/ON/OK/PA
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Re: Info on G3WPO Transverter

Postby G4IRX » Sun 28 May 2017, 21:08

Finally some progress with mine.

Ended up using the BLY34 in the final stage. Initially could only squeeze 400mW out of it but after trial and error I increased the gain of the second stage Q5 by partially bypassing the emitter resistor, giving me a maximum of 800mW.

On to the linear amp which has a SD1274 device fitted. After alignment this produces 20W out for 0.5W drive. There is a problem with the design though - the bias supply is permanently powered (drawing almost 1A on standby!) so I need to add some kind of relay or FET switch to remove this on RX. While I'm doing this I probably ought to do away with the diode and use a two-transitsor bias circuit.
Nick G4IRX
Nottingham IO92JV
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