Ryde Receiver sensitivity comparison

[G4WIM]

Hi,

I've been making the final checks on GB3FT before it goes back into service.
I though it'd be interesting to measure and compare the performance of the rx with that of other users.

For bench marking purposes it's operating at 1249MHz 500Ks FEC 1/2 H265 with a Ryde rx.

The duplexer rx loss is 0.7dB and with -112.6dBm input to the duplexer the Ryde reports D 1.3

I have a high confidence in this number as it's exactly the same as it was 8 years ago when FT was first built !
There is zero tx de-sense which is a good thing.
The preamp after the rx duplexer is nothing special as it uses two PGA103's and the noise figure of the two combined is 1.2dB.

I don't think there's much more I can do to improve the rx, but would welcome opinions and comparisons from other users of the ryde rx.

73 Tim

[g8gtz]

I did a number of tests when I built the original GB3HV Ryde receivers and that sounds pretty good and comparable with what I saw at 333ks.

73
Noel

[G3GJA]

I think you are in the right area Tim.

Your post spurred me into making some tests on GB3EY that I've not done since it was upgraded to totally digital. Using your parameters I ran the output of my PD4 into my antenna with no amplification. I then reduced the output of the PD4's Pluto until the signal display on EY's Ryde showed D1.5.

I then measured the output of the PD4 with an HP 432 bolometer at -7.1dBm. Knowing the feeder losses and the antenna gain at 1275MHz, the EIRP is 15.5dBmW. The distance to the repeater is 10km and is line of site.

Using RadioMobile Online and filling in the known parameters for both ends, the calculator suggests 1µV is being delivered to the preamp input with a 6dB fade margin suggesting the sensitivity is around 0.5µV, the same as your system.

The preamp is a Khune 132A as first used in the analogue GB3EY the late 1990s and from the duplexer loss I guess your filter has the same origin as the one used in EY.

73

Clive

[G4WIM]

Hi Noel

thanks for the feedback and confirmation that it's in the right ball park at least.
I did think about trying to calculate the theoretical threshold but gave up as I was having to make too many assumptions on things like noise bandwidth etc.

Very pleased that it maintains a solid lock right down to a couple of tenths of a dB above threshold. The Ryde / Longmynd code is excellent.

73 Tim