Sunday, 21 June 2015

G11 SDR - Multiband filter board

The multiband filter board for my G11 SDR has been sitting on the shelf for a few months. Last Saturday I decided it was time to get it assembled. The additional board provides Wideband receiver and TX on all HF bands + 6m.

 The first job was to modify the G11 SDR, by removing a couple of relays, doing a small mod around the micro and fitting the jumper cables for the Low Passs & Band Pass filters.
Removing the relays it is a bit tricky, I used the a desoldering pump to remove the solder and help with pliers. The other tricky bit is to solder one of the BPF coax shield to the board on a very densely populated part of board.

Multiband LP & BP filter board
The filter board built is very straight forward, once all the capacitors were accounted for and sorted by value, the only time consuming job is to build the toroids,..lots of them & lots of loops... patience required here. I used the technique with the vice + a chinesse stick ... which saves a lot of time.

Filter board installed in G11 SDR
Once installed, the manual gives you some clues on how to check the band pass filters & low pass filters.

 G8FEK  BBGen - broadband noise generator
I used the G8FEK BBGen broadband noise generator as a noise source to check all the filter operation. In the first instance, I just looked at the S-meter for the 3 conditions explained in the manual - RX1 antena, RX2 antena & Board control cable off.

For fine tuning / minimising insertion loss through the filter board, I am planing to use Noise Figure Measurement software by VK1OD to measure noise power of the audio output - but I need first to investigate how the inductance of the various toroids impacs the pole, zeros & gain at various frequencies of the LP & BP filters.

Calibrating the G11 SDR multiband board

Finally, I checked the sensitivy of the receiver on 10m vs. my Yaesu FT-817 ND using the BBGen and NFM software by VK1OD with an additional laptop as the audio measurement device as per the application notes on G8FEK.

The G11 SDR has better sensitivity than my FT-817 by a few dBs on 10m (both pre-amp on). I need to check some of the other bands. I found this tool useful to look at the sensitivy specs/values

The final step was to calibrate the G11 PA to 10W output power on all the bands.

On the Air:
I got the upgraded G11 on the air on Saturday, as I went into 17m, I heard and logged K8CW on 17m cw. On Sun morning, 10m Es conditions were good and logged on SSB my SOTA friends EA2BD & EC2AG on SOTA summits.

73 Angel

1 comment:

  1. Hi Angel -
    that is a really nice presentation on G11 and multiband filter board.
    Thank you for taking time to document your excitement!
    Posts like this are enormously important for longevity of G11 project.

    I too decided to play with my G11 yesterday. Made dozen contest contacts with JA
    mostly on 15m. Then worked bunch of Europeans on CW on 20m.
    The best DX was VP2MKV, 30m CW which is not easy form my location.
    The icing on cake was qso with ZS4A on JT65. Found him well after sunset,
    still coming in strong via long path over the USA ! With DX like that you have to be quick,
    and in my excitement I forgot to enable TX for the first cycle. Luckily no other callers
    so I got him in the log. ZS is really though one from VK2 on any band or mode;
    I have over 120,000 QSOs in my log and only dozen ZS.
    This was first and only one as QRP.
    Finally, worked KL7QW for 'new one' too, also on JT65.

    Since I got back on air with G11 I've made 60 QSOs on various modes, without really
    working hard. The plan is to reset my DXCC count and see how many countries I can work QRP by the end of the year. Time permited, I reckon I can get 100 DXCC and this is my goal. Making QSOs is as important as building stuff!

    Once again, thank you for your post. The photos are fantastic, and I also envy your clean bench:-)

    73 Nick VK2DX