Adding a 50 MHz (6m) antenna to the remote site

The Red Pitaya can function on the 50 MHz (6m) band. As the remote site is at relatively high elevation of approximately 200 metres ASL the decision was made to install a 6m antenna.

After some research, and reading the blog of GM4FVM, I purchased the Diamond A502HBR. This 2 element Yagi of the HB9CV type promised moderate gain, light weight and a reasonably wide F/B ratio which made it a good candidate for a receive antenna intended for activity detection and monitoring.

A502HBR on the workshop floor

Construction was rapid with so few parts and the use of colour coding on the elements. An initial continuity check of the coax after fitting a PL259 plug showed a connection between centre and braid, which was accepted after acknowledging that the Gamma match will produce this phenomenon with a multimeter – thanks to G0MJI for confirmation.

To mount the antenna, I purchased another L.G. Harris 731 5m pole which, for around £16, offered adequate strength and height for a temporary installation.

The A502HBR on the 5m mast

Not having an antenna analyzer to hand which covered 6m, the initial plan was to start receiving in a variety of modes using the Red Pitayas and see what could be heard. The antenna was fixed on an azimuth of 134 degrees, with the main lobe towards pointing towards Italy.

After a number of hours of silence, I was extremely fortunate to experience a winter Sporadic-E opening that afternoon to test the antenna. First impressions are that it is working satisfactorily.

Signal processing flow
Red Pitaya for WSPR & Red Pitaya for CW and FT8
Stations received on 18 Jan 2018, CW (including beacons) and FT8

2 Replies to “Adding a 50 MHz (6m) antenna to the remote site”

  1. Hi,

    I am very interested in your setup as I wish to deploy a Red Pitaya based listener on 6m. May I ask, did you need to utilize an impedance transformer in the setup? I am weak on RF design and am unsure about this aspect.

    I have an old KB6KQ 6m loop antenna which has worked well for me in the past. I have recently purchased the SV1AFN preamp. I wonder if you have any comment about this setup and if you feel that an impedance transformer is needed?

    thank you

    1. Hi Dave,

      Thank you for your comment.

      I do not use an impedance transformer in my setup.

      I have previously assessed the official Red Pitaya impedance transformer, but found that it did not make a lot of difference. Some of this may be due to my setup being complex with many stages before the RF reaches the Red Pitaya.

      A good website with discussion of impedance and other characteristics of the Red Pitaya is here.

      What modes are you intending to monitor? If CW, the Red Pitaya using the CW Skimmer software still performs better than alternatives. If you are creating a digital monitor, perhaps for WSJT-X modes, I no longer use the Red Pitaya for this and instead use a Raspberry Pi and SDRPlay, running WSJT-X software on the Pi. With this setup, I don’t have to worry about impedance and I can also use dedicated band-specific preamps without complications. Ideally, your SV1AFN preamp should be 6m specific for best performance, but if it is more broadband it still will be helpful.

      Have you already purchased a Red Pitaya? If so, you have nothing to lose by giving it a try. If you have not yet purchased a Red Pitaya, my above paragraph may be pertinent as there may be another way to create a 6m listener which might produce better results.

      Regards,

      Geoff

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