I use Comet CF-4160Ns in the VT ground station. A while back (June of 2016) I measured the insertion loss and isolation for a single diplexer with a calibrated Rhode and Schwarz network analyzer 'on the bench' and the numbers are close to the spec (with a 50 Ohm termination on the 'unused' port for the two port measurements of a three port device).
The claimed numbers are 0.1dB for VHF insertion loss, 0.2dB for UHF insertion loss, and a blanket '60 dB' for isolation. In that controlled measurement situation, for the COM to VHF port path (with a 50 termination on the UHF port) I got 0.048 dB of insertion loss at VHF and 59.695 dB of UHF isolation. For the COM to UHF port path (50 ohm termination on the VHF port) I got 0.100 dB of insertion loss at UHF and 73.812 dB of VHF isolation.
So technically the measured performance did better than the claimed performance on everything except the UHF isolation from the VHF port which only missed the claimed spec by about .3 dB (assuming I didn't screw up the cal process).
All of that though, was for a /single/ diplexer.
I'd have to think more about the ganging of two diplexers on either end of the cable and whether or not you'd actually get the full 'double isolation'. Something about that first diplexer and internal coupling or reflected UHF energy if the there is any mismatch causing UHF energy (from say a VHF third harmonic) leaking back into the UHF radio. Maybe not if you have a good match.....but then coupling at the antennas and an LNA with gain in the mix.........interesting problem to fully think through and sort out the details........
On the surface though, if you had two diplexers, one on either side of the cable, and inserted a UHF signal into the VHF port on one side and then measured the UHF signal power on the VHF port of the diplexer on the other side, there would be about 120dB or so of loss in that path (2 times the isolation plus the cable's insertion loss).......just not sure thats an appropriate test considering that's not quite how the actual system is installed when antennas and LNAs and radios are all in the mix and matches aren't all perfect.
Fun stuff to think about though!
-Zach, KJ4QLP
Research Associate Aerospace Systems Lab Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305
On 1/9/2018 2:18 PM, Robert McGwier wrote:
Since I don't believe the isolation numbers, are they measured or claimed?
Bob N4HY
On Tue, Jan 9, 2018 at 12:10 PM, Floyd Rodgers kc5qbc@swbell.net wrote:
I use diamond mx72n pair to allow a 100 ft run from shack to antennas using 7/8" hardline. .1db loss and plenty of power at 400/250w fm. isolation of the units back to back is 120db uhf/vhf which is plenty to run satellite with two radios and two antennas.
On Tuesday, January 9, 2018 10:22 AM, Paul Stoetzer <n8hm@arrl.net>wrote:
Page 10 of PA1IVO's presentation at the 2011 AMSAT-UK Colloquium includes measurements of the Wimo Diplexer. It appears to have very good specs in general, though it looks like losses were measured at 1.45 dB at 436 MHz, which is a bit high.
https://ivok.home.xs4all.nl/pa1ivo/doc/AmsatColloquium2011.pdf
73,
Paul, N8HM
On Tue, Jan 9, 2018 at 11:16 AM, Rico van Genugten rico.van.genugten@gmail.com wrote:
Hi all,
Thanks for the recommendation Patrick, I have contacted MFJ and hope they will ship a couple of them to the Netherlands. I have also contacted WiMo for some specs on their diplexers as they aren't available on their website, I will share them on this list when I receive them.
73, Rico PA3RVG
On Tue, Jan 9, 2018 at 4:57 PM, Patrick STODDARD (WD9EWK/VA7EWK) < amsat-bb@wd9ewk.net> wrote:
Rico,
I had used either Comet or Diamond diplexers in the past, until I found the MFJ diplexers were about half the price of the Comet and Diamond units, with what I saw as comparable performance. WiMo in the US is like your description of MFJ in Europe; I've never seen or tried WiMo diplexers.
One review I saw a while back actually showed the MFJ-916B to be much better than Diamond's MX-72:
http://www.w4gso.org/news/comparing-duplexers-mfj-vs-diamond/
The pictures and screenshots aren't in this article, but the text tells the story of this comparison.
73!
Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/ Twitter: @WD9EWK or http://twitter.com/WD9EWK
On Tue, Jan 9, 2018 at 9:42 AM, Rico van Genugten < rico.van.genugten@gmail.com> wrote:
Hi all,
I'm using an FT-897D for TX (non-duplex), and an Airspy and computer
for
RX. Good idea to use four switches Greg, in fact that's what I'm
currently
doing. With four switches you always use one antenna for RX and the
other
for TX though, I want to be able to use the same antenna for RX and TX when that works better with the current satellite orientation. Using two switches and two diplexers I would be able to independently select
which
antenna to use for RX, and which one to use for TX. I posted the connection scheme on twitter (warning, mspaint ahead): https://twitter.com/PA3RVG/status/950649511935905792
But we are drifting from the original question: which diplexers? I have heard good stories about the MFJ-916, but its availability is not
great in
Europe. What about Comet, Diamond or Wimo? Are they any good?
Regards, Rico
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