VK5RSC 23cm On Air test

[VK5DF]

Hi All

I have just about finished with the new VK5RSC 23cm Repeater. It is currently on air at my QTH (PF94HW) for testing and would appreciate others trying it out!

Dan
VK5DF

[ADMIN]

You might like to consider submitting a New Repeater Form so that it can be added to the VK Logger Repeater database?

(The form is located in the Logger's upper right under "Contact" link)

Only the following VK5 23cm repeaters are listed:

click for full-size

This makes it very easy for Loggerites to spot things, and for custodians to use the History and Mapping History to view reports.
The Mapping history also makes it possible to view simple terrain profiles, which could be interesting.

Please note that any new Beacon or Repeater submissions require latitude and longitude information (as well as grid square), because as mentioned above, the Google Mapping is an integral part of VK Logger.
(And using the Mapping functionality, it is also very easy to pin point and determine Lat/Lon & grid square, if that is not known.)

Once it is listed, you can always update the location and operating details if/when that happens at your own leisure.

[VK5DF]

Hi all

well on air testing has shown the duplexer is not up to the task. Will have to look at it in depth on tuesday when i can get at the test equipment!

SO off air again

Dan

[VK2XSO]

I had that problem. The duplexer was ok on the bench with a small insertion loss. But put into service it just didn't perform well.
I bypassed it for testing and everything was great. The repeater(s) worked fine without it. The radios used were quite capable of rejecting a 20MHz split I decided that the simplest solution was the right one .... dual antennas.

[VK5DF]

Hi All

I am having issues with the TX de-sensing the RX. I have re tuned the Duplexer and tried again but the problem is still there. with the power set to 1w things seem to work ok, with the power set to 10w its enough to block a user at only a few KM away from my QTH.

Can anyone point me in the right direction with the Duplexer as i am out of ideas and planning to just get a second antenna and be done with it!

Here are the final scans using the Fieldfox!

RX port test

TX port test

The Duplexer in Question

The cable being used is RF-240 for all internal runs to the Duplexer from the radio.

[VK7DB]

The cable being used is RF-240 for all internal runs to the Duplexer from the radio.

I think therein lies part of your problem. Its a bad idea to use dual foil/braid shield coax in duplex installations..

To quote Repeater Builder..
"Cabling: Double-shielded silver-plated coax is the best thing to use to connect a cavitiy to an adjacent cavity in a duplexer, and to connect a radio to a cavity or to a duplexer. For example, RG-214 has two braids made up of individually silver-plated strands and a silver-plated inner conductor for maximum noise rejection. Avoid any coax that has disimilar metals rubbing against each other such as LMR-(any 3-digit or 4-digit number) or Belden 9913, both of which use an aluminum foil shield rubbing against a raw copper braid. Many amateurs have purchased LMR-400 or similar cable, installed it, and it works fine (for a while). They just rave about how good it is. Then anything from 9 months to 5 years later they find themselves taking it down as the cable itself causes "duplex noise" (see the article on this page titled "Help!! I have a crackling noise in my repeater" by Kevin Custer W3KKC). The expensive LMR cable gets reused somewhere else (in any simplex situation). RG-142 and RG-400 are both a smaller version of RG-214 (but sharing the same construction) and can also be used (but see the article on this page titled "Double Shielded Coax Cable, the differences between RG-142 and RG-400, and why you DON'T want to use RG-142..." by Eric Lemmon WB6FLY)"). My personal preference is to use RG-214 as the top-of-the-tower antenna-to-Heliax jumper, nothing but Heliax and Superflex on the antenna side of the duplexer and nothing but Superflex and RG-400 on the radio side. Yes, it's expensive, but like my late father used to say about hand and power tools, "Buying quality only hurts once". Good quality cable with the right connectors is going to be low loss and last a long, long, long time, and it's one less thing to worry about. If you have to use coax in a duplex situation then look at RG-214 or RG-393 for the large diameter (i.e RG-8 / 213 / 214 size) and RG-142 or RG-400 for the small diameter (RG-58 size). All are double shielded with silver plated shields and will not cause duplex noise."

http://www.repeater-builder.com/antenna ... exers.html

[VK7DB]

I just found a build photo of the repeater and it looks like you have used RG142 or RG400 on the duplexed antenna port, so my previous post is irrelevant..

[VK4TI]

""The cable being used is RF-240 for all internal runs to the Duplexer from the radio."" , I suggest you check in the repeater groups as it's common knowledge disimilar foil braid coax causes problems as previously desribed , changing the internal cables to a dual braid silver plated style coax like RG214 / superflex wont unreasonable and should assist considerably , contact Eric Lemon directly for conformation
B

[VK5GR]

Dan, contact Colin VK5ACE who built the Summertown 23cm repeater to see what he did with cavities. He might be able to give you some tips.

Looking at your plots, I'm also not sure that your notches of only -80dB odd are enough. If you are running 10W you have +40dBm input - so you are only going to drop the TX to between -40 to -50dBm in terms of de-sense. Most receivers probably only can do -60dBm rejection so you are down at perhaps -100 to -110dBm - BUT your receiver threshold is about 10-15dB better than that with say a 0.3uV receiver equating to something around -120 dBm from memory.

Separate antennas can buy you another 20dB if placed properly on the structure which would solve it - or you need to find a better duplex combiner block. If you are running co-linear antennas on the repeater and are transmitting and receiving on the same antenna you also need to be very careful with the type of antenna. Diamond home base antennas for example are a no no - their construction creates too many non-linear joints and hence leads to IMD production.

Regards,
Grant VK5GR

[VK5DF]

Hi

Thanks for the information. I have been a bit busy off lately so haven't made any progress. I will have another go this weekend.

For info the clubs antenna is one of those Diamond antennas!

Will see what happens and post more soon.

Dan
VK5DF

[VK7HH]

Daniel,
When do the club expect to have the 10m repeater back on the air?

[VK5DF]

10M... that's a different case and in the list of stuff to do....

Good news is that someone else is looking into it as well.

No no answer on that yet!

Dan

[VK7HH]

10M... that's a different case and in the list of stuff to do....

Good news is that someone else is looking into it as well.

No no answer on that yet!

Dan

What broke on it?