Re: Desense is driving me crazy

#215551

Q cavity works just as well as a pass can. I’ve tuned 6 can Q duplexers so that the can closest to the equipment is a symmetrical notch to give it a good pass response so other stuff outside the ham band is filtered out. The other 4 cans tuned as a 4 can duplexer with 0.7dB insertion loss per can.?

Re: Desense is driving me crazy

#215550

开云体育

I made several kits at the shop for the internal desense problem.?? Due to the cable routing, I used RG-223.?? It is more flexible than RG-400.

Electrically, either one would work, but I liked the lay of RG-223 better.

For the Q202, the high split harness with not tune up correctly.?

At this point, I would eliminate the well known TX additional noise floor of that repeater by using a different repeater.??? You could also try a bandpass only cavity after the TX.?? A BPBR will not work, it must be BP only.?? The cable length is critical for a good match, but at least you can see if it helps the problem.?? Jeff could probably give you the correct jumper length if he has the cavity information, if you end up going that direction.

John?

Show quoted text

On 2025-05-25 17:58, N4FOX via groups.io wrote:

Al,

Thanks for the thought about that.

I covered that in one of my earlier post. I replaced those cables with RG400 a while back.?

?

Re: Desense is driving me crazy

#215549

Al,

Thanks for the thought about that.

I covered that in one of my earlier post. I replaced those cables with RG400 a while back.?

?

Re: Desense is driving me crazy

#215548

Has anyone mentioned in-cabinet desense? Some of those Yeasu DR series had cheep RG58 internal RF cables. Try hooking the transmitter direct to a dummy load and the receiver to a frequency generator and see if there is any difference with and without the transmitter on. Eliminates the duplexer, feedlines, antenna, etc.

?

Al, k9si

Re: Desense is driving me crazy

#215547

Mick,

?Actually no i didn't. Once I was told it wouldn't be ideal I pursued getting or making one that was.?

?

I still have it. Though I adjusted the can layout/order a little to allow the new harness to flow around better.

?

I've actually considered trying it being I've had all these other issues.?

?

I'll share some pictures of the original harness vs what I made. The with & without the door.

?

Re: Desense is driving me crazy

#215546

Did you ever try the original harness?

Mick - W7CAT

Show quoted text

----- Original Message -----
From: "N4FOX via groups.io"
To: [email protected]
Sent: Sunday, May 25, 2025 01:10:37 PM
Subject: Re: [repeater-builder] Desense is driving me crazy

Harold,
I know you're right there. I didn't want to do this with so many connections. I liked the harness the duplexer came with. I was told/advised it was just not the right length being the duplexer was originally tuned around 170mhz. Then going down to 145.330 MHz.

I have tried calling & emailing Sinclair to ask about getting the correct harness from them. They just never returned my calls or emails. Whats odd is I've heard several stories about how Hams have got help from Sinclair & they were happy to help out. One fella told me he talked to a Mr. Sinclair about some duplexers years back. Idk if that's true or not but it sounded nice.

This is the sheet they came with. Idk if this is from Sinclair directly, but looks like someone bought them through tessco originally.

As for the VNA on the ground for $850. Sounds like it need to get to some ham fest lol. I quit going years ago. I used to have friends to go with. But they aren't around now days. They have either passed away or got out of the hobby.
It's not much fun doing things solo. To me life is about the experiences. It's fun to share them. Otherwise it feels like what I'd image drinking alone is like..lol. idk, I don't drink.

-- 
Untitled Document

Re: Desense is driving me crazy

#215545

I remember receiving several factory tuned Q-2330 duplexers from Sinc. and seeing exactly what you describe when viewing the RL. I called and spoke to an engineer and was told that what I was seeing was "normal". When installed and tested the system worked as it should, so I did not give it another thought.

Larry

Show quoted text

On Sun, May 25, 2025 at 11:18?AM N4FOX via <N4fox.r=[email protected]> wrote:

Harold,

?Thanks for sharing your insights. I appreciate that. I do see 3 humps in the return loss when the cans are all hooked together. It's always kinds bugged me, but I was told it's normal by several folks. So it put my mind at ease a little.?

?

I have tried listening for desense by taking the duplexer out of line completely. It's not present then. It sounds exactly how I'd imagine it to sound. No change in the receiver at all when the transmitter is engaged, no matter what power setting is used.

Re: Desense is driving me crazy

#215544

Right or wrong, I have a M1225 programmed for the frequencies. I use it for the final notch tuning. I just keep turning down the signal from the service monitor and tune until it goes away and then turn it down some more.

Mick - W7CAT

Show quoted text

----- Original Message -----
From: "N4FOX via groups.io"
To: [email protected]
Sent: Sunday, May 25, 2025 12:14:23 PM
Subject: Re: [repeater-builder] Desense is driving me crazy

Mick,
I've wondered the same thing. I started off with a Lite VNA 64. It was regarded as the best small handheld inexpensive VNA at the time of purchase a few years ago. It was only about $150. It's really cool for what you get vs cost. Handy..

When I decided to get into tuning these cans & to have some more equipment I looked into other devices. From 30yr old professional equipment with floppy drives & CRT displays to newer VNA within the budget. The 2nd device I picked up was called the LibreVNA for about $600. It's a two port VNA that hooks to the PC & software as a means to view things. That gave me 90/100db of dynamic range. Plus it was easier to navigate & set things up like markers & more over the Lite VNA 64. I knew the duplexer would exceed the dynamic range of that device. So I ordered a Siglent SSA3021X + Spectrum analyzer with TG for about $1800. To try & help get the rejects dialed in. Plus I figured it would be useful for the hobby. I used those to tune the duplexer. Then here just a couple months ago I picked up a Measall KC901J dual port VNA for about $1300. It's pretty nice & has lots of extra features as well. It's still only 100db of dynamic range. It's appeal to me over the LibreVNA was It's a self contained unit with It's own display.? Plus it was highly regarded by several people as being good quality for the cost. I've actually seen it go past 100db of dynamic range in these lower VHF ranges of 2M.

I know all together I spent a good bit for all 3 items. I could of probably got a pretty good used old VNA. I don't really regret it though. I have some poor luck. I'd probably buy an old one then have something fail on it that's hard to get replaced. ??

-- 
Untitled Document

Re: Desense is driving me crazy

#215543

I would like to have had that one. I'm sure someone grabbed it and paid a little less for it.

Mick - W7CAT

Show quoted text

----- Original Message -----
From: "Harold Farrenkopf via groups.io"
To: [email protected]
Sent: Sunday, May 25, 2025 12:24:41 PM
Subject: Re: [repeater-builder] Desense is driving me crazy

I saw a used Agilent 8753d with all the goodies in it (6ghz and tdr) sitting on the grass at Dayton this year for $850. I commented to him that it should be respected more and put on a table….. ?:)

-- 
Untitled Document

Looking for a connector

#215542

I’m looking for the connector to go on the back or the whole cable kit for a dc backup on a quantar. Does anyone here have anything they would be willing to part with? I can’t find anything online. Thanks!?

Re: Desense is driving me crazy

#215541

Harold,

?I know you're right there. I didn't want to do this with so many connections. I liked the harness the duplexer came with. I was told/advised it was just not the right length being the duplexer was originally tuned around 170mhz. Then going down to 145.330 MHz.?

?

I have tried calling & emailing Sinclair to ask about getting the correct harness from them. They just never returned my calls or emails. Whats odd is I've heard several stories about how Hams have got help from Sinclair & they were happy to help out. One fella told me he talked to a Mr. Sinclair about some duplexers years back. Idk if that's true or not but it sounded nice.

?

?This is the sheet they came with. Idk if this is from Sinclair directly, but looks like someone bought them through tessco originally.?

?

As for the VNA on the ground for $850. Sounds like it need to get to some ham fest lol. I quit going years ago. I used to have friends to go with. But they aren't around now days. They have either passed away or got out of the hobby.?

It's not much fun doing things solo. To me life is about the experiences. It's fun to share them. Otherwise it feels like what I'd image drinking alone is like..lol. idk, I don't drink.

?

Re: Desense is driving me crazy

#215540

I saw a used Agilent 8753d with all the goodies in it (6ghz and tdr) sitting on the grass at Dayton this year for $850. I commented to him that it should be respected more and put on a table….. ?:) ?

?

Re: Desense is driving me crazy

#215539

There are also a lot of RF connections being made with all those T connectors as opposed to a one piece crimped and soldered together harness.?

In commercial and public safety systems, a 3dB degradation was acceptable. ?In fact, on VHF, site noise was a major factor before any transmitters were keyed. I’ve seen some sites as high as 18dB and they wondered why those were deaf.?

Re: Desense is driving me crazy

#215538

Mick,

?I've wondered the same thing. I started off with a Lite VNA 64. It was regarded as the best small handheld inexpensive VNA at the time of purchase a few years ago. It was only about $150. It's really cool for what you get vs cost. Handy..

?

When I decided to get into tuning these cans & to have some more equipment I looked into other devices. From 30yr old professional equipment with floppy drives & CRT displays to newer VNA within the budget. The 2nd device I picked up was called the LibreVNA for about $600. It's a two port VNA that hooks to the PC & software as a means to view things. That gave me 90/100db of dynamic range. Plus it was easier to navigate & set things up like markers & more over the Lite VNA 64. I knew the duplexer would exceed the dynamic range of that device. So I ordered a Siglent SSA3021X + Spectrum analyzer with TG for about $1800. To try & help get the rejects dialed in. Plus I figured it would be useful for the hobby. I used those to tune the duplexer. Then here just a couple months ago I picked up a Measall KC901J dual port VNA for about $1300. It's pretty nice & has lots of extra features as well. It's still only 100db of dynamic range. It's appeal to me over the LibreVNA was It's a self contained unit with It's own display.? Plus it was highly regarded by several people as being good quality for the cost. I've actually seen it go past 100db of dynamic range in these lower VHF ranges of 2M.?

?

I know all together I spent a good bit for all 3 items. I could of probably got a pretty good used old VNA. I don't really regret it though. I have some poor luck. I'd probably buy an old one then have something fail on it that's hard to get replaced. ??

Re: Desense is driving me crazy

#215537

The older bulkhead barrel connectors that had glass and hermetically sealed had intermod generating material in the pass through so that temperature changes didn’t break the glass. ?

Try a different load that can handle the power. ?

another method but used for intermod testing instead of noise was to put good low intermod lossy long cable between the load and the device under test to act like a 10 to 20dB pad before the load and that reduced the intermod generated by the load. ?But that takes quite a bit of cable at VHF.?

Re: Desense is driving me crazy

#215536

I never testing the one I have, but have wondered how close many of them may be.

Mick - W7CAT

Show quoted text

----- Original Message -----
From: "Harold Farrenkopf via groups.io"
To: [email protected]
Sent: Sunday, May 25, 2025 11:43:00 AM
Subject: Re: [repeater-builder] Desense is driving me crazy

The tiny VNAs are pretty accurate in frequency- at least the ones I’ve used and if they are off 5khz, it wouldn’t affect it much.

-- 
Untitled Document

Re: Desense is driving me crazy

#215535

Harold,

?I will give that method a try with taking the tee out of the antenna port. Then using different dummy loads. The picture below is the main dummy load I've been using for reference (TX/RX). The others I have are the finned smaller screw on type. Then some other lower wattage (1-5wt) ones I use when testing things with the VNAs. Pics below.

?

Im not certain what isolation yaesu recommends. The repeater is 5 to 50 watts. I prefer to run it at 5 watts into a motorola msf5000 100 watt PA. Because those amps are real workhorse that doesn't hardly break a sweat. For reference though in the video the PA was bypassed so it was just the 5/20/50 watt settings of the repeater itself.?

?

Im using RG214U cables for the repeater harness. Then RG400 from the repeater to the duplexer. I have also tried RG214U from the repeater to the duplexer. There was no difference between them other than a tiny difference in db loss per cable. Also using RG214U from antenna port to the dummy load. As for antenna it's all 1/2 Andrew's heliax.?

?

I do have bulkhead N barrels on the cabinet door. But I have not used the door yet. I've been bypassing that door & have it removed for now.?