Is GB3TV working?

[g0mjw]

No Pluto involved - this is a minitiouner sitting on the IF of my IC9700 so already filtered.

What I think is happening is the 23cm preamp is seeing signal at 437 MHz and it doesn't have enough front end filtering to prevent that causing non-linearity. Because 3x437MHz = 1311MHz there is also a high possibility that the 3rd harmonic of the TX is a problem.

If you think about it, the signal being received is weak. Of the order of -120dBm. With a TX power on 70cm of 1W (30 dBm) a suppression of up something like 150dB would be needed to reduce the level. If the suppression were "only" 120dB it would still be too much for the minitiouner not to be de-sensed by a strong signal only 7 MHz away. Even if the TX is perfect, there are non-linearities in everything where that very low level harmonic might be generated. There are probably protection diodes in the pre-amp that would be prime suspects.

Mike

[M0DQW]

Ahh yes, that makes sense for your setup. I do not have a pre-amp on my 23cm beam.

I guess with literal line of site, across the fields to me, GB3TV is a lot stronger.

It was nice to test the big amp on 70cm and get a signal in just using my vertical. Think I could get it with around 50 watts using the vertical. Would be way less if I was using the beam, which I will defo try soon. Although, the little small 70cm amp I made worked great too with the beam.

Cheers
Matt

[G4HTZ]

Just wondering what the improvements have been on 70cms …..not a good path from here

[arthur21]

GB3TV batc stream is now up and streaming.
73 Arthur
G4CPE

[arthur21]

Hi Steve
We have fitted a filter and preamp to the 70cms input to the ryde receiver The receive aerial is a 70cms loop made for us by G8ADM a long time ago and still working well.
73 Arthur
G4CPE

[G4HTZ]

Hi Steve
We have fitted a filter and preamp to the 70cms input to the ryde receiver The receive aerial is a 70cms loop made for us by G8ADM a long time ago and still working well.
73 Arthur
G4CPE

Thanks for information….not a good path from here nr Sudbury….GB3DUN weak even with 36 ele and mast head LNA

[g0mjw]

Just wondering what the improvements have been on 70cms …..not a good path from here

Very sensitive, I think I might even get in from Bolton.

Mike

[g0mjw]

Ahh yes, that makes sense for your setup. I do not have a pre-amp on my 23cm beam.

I guess with literal line of site, across the fields to me, GB3TV is a lot stronger.

It was nice to test the big amp on 70cm and get a signal in just using my vertical. Think I could get it with around 50 watts using the vertical. Would be way less if I was using the beam, which I will defo try soon. Although, the little small 70cm amp I made worked great too with the beam.

Cheers
Matt

All that trouble to build a 500W PA and it only needs 1w

[G4HTZ]

Does anyone have a qra locator for GB3TV ….i mean a 8 figure one ….so I can do some accurate path plots from here ….got one of Jim’s 70cms pallets and 18 ele powerbeam …so plenty of erp

[arthur21]

Locator for GB3TV is IO91RU59 and the aerial is about 12m agl
Give it a try you may get into the repeater and we now have a stream which you can watch for your tests.
73 Arthur
G4CPE