THE LISTENING POST.
- Thread starter BillC
- Start date
VK3EB
Active member
Big day out at the Listening Post or should that be the Listening Cubby House. (see photo)
We have three SDR's working, Strathy 1 and 2 currently public and listed on KIWI SDR map and list. Strathy 3 (flydog) is mainly for club members (is public but need direct URL.) No time out limit set on unit, will be used for testing other antennas etc.
Several ways to log on.....http://kiwisdr.com/.public/
Just enter VK3SOL in search box.
OR
Flydog
listen.sadarc.org bit more noise than other Rx's
Bill already has plans for new mega loop so stay tuned.
Happy listening.
Dallas
We have three SDR's working, Strathy 1 and 2 currently public and listed on KIWI SDR map and list. Strathy 3 (flydog) is mainly for club members (is public but need direct URL.) No time out limit set on unit, will be used for testing other antennas etc.
Several ways to log on.....http://kiwisdr.com/.public/
Just enter VK3SOL in search box.
OR
Flydog
listen.sadarc.org bit more noise than other Rx's
Bill already has plans for new mega loop so stay tuned.
Happy listening.
Dallas
A nice sunny day, Dallas and I raised the first pole of the horizontal loop, the pole 11 meters high, the mounting stump six feet in the ground, the bolts 20 mil., sheave and halyard fitted before raising the pole. Three more poles to raise before we hoist hoist and connect the loop wire.
Yes Ray we used the Nano VNA , pretty good at 1.8 mhz , with a few peaks across the spectrum , can't be too specific. Generally as expected quite a lot lower noise floor with increased signal level. Had some MW band cross modulation, have just now switched in 8 db of attenuation at the REDGUM receiver input. See what you reckon, cheers.
Listening to VK3HK 1825 AM this morning, kiwi is doing a couple of S points better than redgum. I think it was the other way round last night.
It might just be the 8dB attenuator?
Also redgum seems more sensitive generally. It will be interesting to see the SNR rankings between the two.
So, in summary both antennas working brilliantly.
It might just be the 8dB attenuator?
Also redgum seems more sensitive generally. It will be interesting to see the SNR rankings between the two.
So, in summary both antennas working brilliantly.
Hi Ray, We think that the loop output level is a bit higher than the dipole, it also seems to have a slightly lower noise floor than the dipole, and if checking an end to end spectrum sweep the waterfall appears to show more signals than the dipole. However the published SNR. figures do not show a better performance.However as you say both antennas work very well, possibly under certain circumstances one of the antennas may out perform the other. We will stick with them for a while. There will be minor adjustments to balun transformers and feed lines as we progress. Thanks for the report. We will be listening. Out.
I am working on a matching transformer from loop to co ax, also spark gap and bleed resistors for voltage discharge to ground. Given that the loop wire is fully floating above ground and would have capacitance to ground I presume that it could generate a charge due to wind / air friction or rain static charging etc. So I have included spark gaps set at .0015" and , two 220k resistors for continuous discharge to ground. I hope that 110k is a high enough resistance to not upset the RF side of things. The spark gaps should fire with a peak pulse, and if the antenna itself is struck by lightning the wire will vaporize at 400 amps!! . I will have to find some heavy duty copper cable for the grounding connection. Do you think that might work Ray, Dallas , Denys & ? Check the image.
Thanks Denys , the screens should be good too. Just a note for users about RedGum SDR , because the loop ant. develops a high RF voltage it tends to overload the receiver up to and around 2.5 Megs , so at the present time I have in the hut a switched attenuator in the coax feed to RedGum with 5 db switched in. I leave this in always but at night time I switch in another 3db using the receivers own internal attenuator via the on screen control. I think that other users would be able to alter that attenuation setting too. However ANY LESS than a total of 8db will result in overload generated by several strong medium wave AM stations.
Hi Bill, The antenna winding on the toroid should provide a DC short, so that would stop some electrostatic buildup. And tend to provide some protection for the reciever front end.
The intermod problem that is obvious on the big loop, is a tricky problem to solve. The antenna is very sensitive and getting hammered,
If you have worked out what MW stations are the culrpits, maybe a notch filter is required.
The intermod problem that is obvious on the big loop, is a tricky problem to solve. The antenna is very sensitive and getting hammered,
If you have worked out what MW stations are the culrpits, maybe a notch filter is required.
Thanks for the comments Ray. I have seen a complicated filter design which provides low frequency roll off starting at about 4 meg and working down from that position, but it attenuates all the long wave bands too. so I will try some trap filtering when I get a chance. There is still a lot of work to finish the project.
Last edited: