Search found 198 matches

by vk7jj
Wed Jul 17, 2019 8:27 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 103
Views: 11405

Re: Receive Antenna & Impedance "Matching"

Hi Gianfranco, sorry about the delay in replying to your other points, been choring. Thanks for you very kind offer regarding the crystals, while only a single crystal appears to give the required bandwidth, like a lot of other radio commodities we took for granted they have become very expensive. W...
by vk7jj
Wed Jul 17, 2019 7:53 am
Forum: SDR Antennas
Topic: A FOOLPROOF ANTENNA SWITCH
Replies: 35
Views: 7477

Re: A FOOLPROOF ANTENNA SWITCH

I wonder how the MFJ-1708 antenna Tx/Rx switch (and it's variants) would stand up to the same level of scrutiny, relays included. Featuring prominently in these pages and with an application note on the SDRPlay site, no less! MFJ-1708.png I've several MFJ products in the shack and while they have be...
by vk7jj
Tue Jul 16, 2019 12:39 am
Forum: SDR Antennas
Topic: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna
Replies: 66
Views: 3445

Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

I am thinking of an all stainless steel (or copper) square A quick note on stainless, here is a pic of a full size 160m delta using copper, aluminium and steel wire. Copper is line 1, aluminium line 2 and steel line 3. Wire radius is 0.8mm in all cases. Screen Shot 2019-07-16 at 10.36.29 am.png Loo...
by vk7jj
Tue Jul 16, 2019 12:27 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 103
Views: 11405

Re: Receive Antenna & Impedance "Matching"

Hi Gianfranco I do have an RSP2 but I can't run it and the RSP1A simultaneously with SDRuno because of my lack of Windows boxes and I did put an RSP2 through it's paces using it's high impedance input a couple of pages back, threads progress too quickly! After many days of testing, comparing the FT-...
by vk7jj
Mon Jul 15, 2019 11:52 pm
Forum: SDR Antennas
Topic: A FOOLPROOF ANTENNA SWITCH
Replies: 35
Views: 7477

Re: A FOOLPROOF ANTENNA SWITCH

This looks like the data sheet for Glovisol's relay, follow the link below and then click the "Download PDF" button https://www.radiolocman.com/datasheet/pdf.html?di=135545 Contact material = Silver alloy AgCdO、AgSnO2、AgNi Contact resistance = 100mΩ(1A 6VDC) Sealed construction as opposed ...
by vk7jj
Mon Jul 15, 2019 10:54 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 103
Views: 11405

Re: Receive Antenna & Impedance "Matching"

.. pity about the page break, I'd better post the comparison pic again Here is the Kenwood jj-high.png Here is the RSP1A jj3-high.png c) From the spreadsheet analysis of the many hundreds of spots from the last 24 hours it appears the RSP1A's WSPR noise floor is -29dB as compared with -33dB from the...
by vk7jj
Mon Jul 15, 2019 10:31 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 103
Views: 11405

Re: Receive Antenna & Impedance "Matching"

OK, I have finished comparing an RSP1A with a good conventional receiver on WSPR 40 meters, a Kenwood TS-120s with GPS-DO VFO. Despite all my spreadsheets of results it boils down to just a few things: a) a few dB of SNR makes a very large difference to hearing very low level signals. It's worth rem...
by vk7jj
Mon Jul 15, 2019 10:13 am
Forum: SDR Antennas
Topic: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna
Replies: 66
Views: 3445

Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Let's get back to antennas, wonderful things that they are. Yes, I bet you can't wait to have a play with longer lengths of wire at home. Even if we all lived in a perfect noise free environment there is clearly a point where the desired signal voltage from a small antenna falls below the level wher...
by vk7jj
Mon Jul 15, 2019 9:47 am
Forum: SDR Antennas
Topic: A FOOLPROOF ANTENNA SWITCH
Replies: 35
Views: 7477

Re: A FOOLPROOF ANTENNA SWITCH

"General Purpose relays are just that general purpose." Hi Mike, making generalisations tells us nothing at all about any particular relay. The relay pictured is not an unbranded unkown it is branded "Songle" and is said to be sealed. Have you had a go at finding the specs of th...
by vk7jj
Sat Jul 13, 2019 10:58 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 103
Views: 11405

Re: Receive Antenna & Impedance "Matching"

Update: 12 hours of RSP1A versus TS-120S revealed the TS120S as clear winner with typically 10 to 15 percent more spots. Rather than let that experiment run for a full 24 hours I put a new and better toroid preselector inline with the RSP1A. Over the last hour that has more than reversed the spot co...

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