CTCSS Reverse Burst?

[btu44]

I'm almost finished installing a CTCSS encoder module in my Optima Mk3. I'm hoping it will let me connect to the 10m band of the N6Lxx repeater system here in my area.
The CTCSS module can be setup for a simple CTCSS tone or CTCSS with reverse burst. I have googled the N6LIZ repeater and have not seen anything other than its PL is 107.2.

Any ideas if I should configure the SS-64 CTCSS Encoder with reverse burst or with out?

Thanks,
Barry

 

[KC9Q]

All reverse burst does is provide a 180 degree phase reversal of the PL tone for a 250 ms time period when the PTT is released. It was provided to eliminate any trace of squelch tail from the speaker. It only applies if you have the receiver decoding the PL tone. You'll know it is working if you hear a soft click-click sound out of the speaker when the PTT is released.

 

[fourstringburn]

The few 10 meter repeaters out there I ever encountered do not require reverse burst for the PL tone and/or different tones for encoding and decoding.

Good luck with your install!

 

[btu44]

Good news, I'll setup the simple way first. If there are problems I can set up later with a reverse burst.
Now the harder part is getting my General so I can use it

Not that I think many people will need a CTCSS on an export radio but here are a few pics on this project.

These mods are on a MC-46 aftermarket microphone. It works well with the Optima

Here I moved the caps to the board the make room for the CTCSS board. I glued some wheel weight to give the mic some heft.

I used Velcro to hold the CTCSS to the main PCB.

The Optima has an unused pin in the mic connector that I used to route the CTCSS tone. I added the violet wire used pin 4.

The tone wire is connected to the FM Mod VR303, the pin closed to the shielding.
Big thank you to Mike at Yeticomz for the help with this project.

Here it is all wired up. Pin 5 on the CTCSS connector was not used in the end config.

 

[fourstringburn]

Looks like you just about nailed it.

I have an encoding PL tone board installed on my RCI 2950. I also own 2 President HR2600's and they were both manufactured with tone boards so it's not too uncommon to have them on export radios.

Good luck on your General class!

 

[btu44]

Good luck on your General class!

Thanks, I think I'll need it. The section on digital modes is kind of a blur.

 

[btu44]

Well I thought I had this setup just right and all was good. 10 meter repeater audio sounds great and was able to 'kerchak' the repeater once, but today I heard some 10meter USB voice and it sounds terrible.

See short video:


What I don't show on the video is the CTCSS tone distortion at the FM Mod pot. (The vid show the tone at the microphone). It looks fine when the mic is not keyed. When the mic is keyed there is a +2 VDC bias and the tone gets distorted. It looks like oscillation at high frequency. With the o'scope at .02 uS time div., it is un-syncable. The oscillation amplitude is about half the tone amplitude. I was hoping it was that the o'scope ground lead was kind of long and that was the source of the noise.

I'm thinking about using small diameter coax cable instead of the violet wire entering the radio. Maybe this would provide shielding. But I don't understand why the tone is affecting SSB?

Anybody have some other ideas?

 

[Captain Kilowatt]

The tone should not be active in SSB mode. Standard injection level is 10% modulation BTW and that could be enough to be heard on SSB.

 

[btu44]

The tone should not be active in SSB mode. Standard injection level is 10% modulation BTW and that could be enough to be heard on SSB.

I did a few measurements with the o'scope. I measured the audio signal at the FM Mod pot while saying 'check-check-check'. I measure a max of 1.5V Pk-Pk. Originally the CTCSS tone was set to .5V Pk-Pk on the above video. So I adjusted it down to 150mV (10% of 1.5V).
Does this sound right?

 

[Captain Kilowatt]

Ideally you want a deviation meter to measure the FM deviation. With +\- 5 KHz of deviation you want about +/- 500 Hz of deviation from the CTCSS tone. Failing that you could use a receiver with a AF volt meter or scope across the speaker and adjust for 1/10 of the voice peaks but that is only ballpark as it assumes that the voice peaks are exactly 5 KHz. The same caveat applies to your method above. It may work and as long as the CTCSS tone triggers the repeater without the tone being heard too loud under the voice it should be OK.

 

[btu44]

It may work and as long as the CTCSS tone triggers the repeater without the tone being heard too loud under the voice it should be OK.

This is how the manufacture of the tone encoder said to set the tone level. Find the middle were it just triggers the repeater or can be heard by the listener. I'll just wait till I have my General and see how it goes. If all else fails the guy at Radio shop said he'd align it for $40.
I have a 8 position half pitch DIP switch on order. I'll use it to disconnect the tone when it is not working the repeater. Not terribly convenient but workable. This should fix the SSB distortion.

Thanks for all the help.