Hi all,
First of all, thanks for your patience. Still learning!
Well, until few days ago I have been able to do many contacts throught SO-50 using my Baofeng UV-5R and Elk antenna in half duplex.
I wanted to go next step and try Full Duplex so I bought a Midland CT 890 Full Duplex handy (129 eur).
I can tell that the Midland receiver seems much better than the Baofeng one. I have been able to work (still half duplex) even when the satellite was a few degrees over the horizon. The Baofeng seems much deaf than the Midland, but this my subjective experience. The measured sensitivities I got from a review are: 0.179 uV (12 dB SINAD) in VHF and 0.205 uv (12 dB SINAD) in UHF but I don’t have the Baofeng values. If somebody has them It would be nice if you share so we can compare.
I have checked that the Full Duplex mode works by transmiting with it and at the same time receiving a signal from the Baofeng UV-5R but all this using the whip antenna that comes with the Midland.
The problem comes when I connect the Elk antenna to it. If I press the PTT the receiver noise goes to maximum. I tried to make a contact with the SO-50 but I could not hear anything when I pressed the PTT. All was noise. I had to disable the Full Duplex and then I was able to make some nice contacts (EA1JM, CU2ZG…) in half duplex.
So my questions are…
1. Is it possible to use a single Log Periodic antenna (only one feed point) as the Elk to work Full Duplex or two antennas are needed?
2. In case that it is possible… Would this improve by using separate receiver and transmitter with a filter that gives a feed point for VHF and another one for UHF? (the Elk antenna only has a feed point)
I have to make more tests but at first time, It does not seem possible to use the Midland CT 890 (and maybe other full duplex handys?) with the Elk antenna in Full Duplex…
Thanks. Any comments are always welcome
Felix EA4GQS
El 16/12/15 a las 16:59, Felix Paez escribió:
The problem comes when I connect the Elk antenna to it. If I press the PTT the receiver noise goes to maximum. I tried to make a contact with the SO-50 but I could not hear anything when I pressed the PTT. All was noise. I had to disable the Full Duplex and then I was able to make some nice contacts (EA1JM, CU2ZG…) in half duplex.
Hi Felix,
Probably you are experiencing desensing on the receiver caused by the transmit signal. This is much worse when working V/U because the 3rd harmonic of the TX signal lies on the 70cm band. Patrick WD9EWK has made many tests with different inexpensive Chinese full-duplex radios and it seems that most of them are fine to work AO-85 (which is U/V) but it's impossible to work SO-50 with any of them. Perhaps you could have more luck with AO-85.
So my questions are…
- Is it possible to use a single Log Periodic antenna (only one feed
point) as the Elk to work Full Duplex or two antennas are needed?
Yes. It's technically possible, although, as I said, desense can be an issue. I think that it's worse with the elk than with, say the arrow (which is two crossed yagis) because the coupling between the TX and RX is much greater on the elk than on the arrow.
In case that it is possible… Would this improve by using separatereceiver and transmitter with a filter that gives a feed point for VHF and another one for UHF? (the Elk antenna only has a feed point)
If you have a 2m/70cm duplexer, you can try using two radios. Perhaps a cheap Baofeng for TX and the Midland (which is more sensitive) for RX. This will probably be much better than just using the Midland full-duplex, because the external duplexer will provide better isolation than the one on the Midland.
I have to make more tests but at first time, It does not seem possible to use the Midland CT 890 (and maybe other full duplex handys?) with the Elk antenna in Full Duplex…
It seems that it's difficult to get a handheld that can do V/U full-duplex. However, U/V is much easier.
73,
Dani M0HXM/EA4GPZ.
participants (2)
-
Dani EA4GPZ -
Felix Paez