pl reverse phase

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beamwidth
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Joined: Fri Feb 27, 2004 8:15 am

pl reverse phase

Post by beamwidth »

Does anyone know of an aftermarket pl board which will work with the ht1000 and mts2000 as far as the reverse phase is concerned? We get the squelch tail after each unkey and users prefer not too hear this.

Unlike Ge, Kenwood, Vertex ..... they just need a phase shift, but the big M needs a reverse phase of 120 degrees at about 180ms. thanks john
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batdude
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..

Post by batdude »

not to sound like a :o head

but

tell the guys to buy a motorola repeater.... end of squelch noise


there are no aftermarket boards made that i know of that will interface to the jedi .... no one ever made them for jedi since the radio has pl/dpl standard!

doug
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beamwidth
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Post by beamwidth »

I should have said they have nothing but the big M in portables and mobiles. The aftermarket board would have been for the base stations.

They right now use mast II base stations, these put out the reverse burst at 135 degrees and work perfect with the big M. No squelch tail at all. They are just trying to update all base EQ with different vendor. But with this tiny problem I will push them towards Moto base stations. I guess GE is the only vendor that used to make the reverse phase work by getting close enough to their 120 degrees. 180 degrees won't cut it. The Motos have about +- 30 degrees of latitude in which they will work. thanks again for your help
mastr
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Post by mastr »

The communications specialists ts-64 does both reverse burst and PTT delay. It has been on the market "forever", and so documents probably exist somewhere to show hook up to just about any mobile or station.

I'm not sure what the phase shift is , but with adequate PTT delay that shouldn't be much of an issue.
Will
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Post by Will »

Most non Motorola brands do not get the "reverse burst" close enough to what Motorola (still) uses. To go 'way back' in time when Motorola came up with PL, CTCSS, they used mecanical reeds that had a way different damping requirement to 'stop' the vibration and hence the decoding. Along came solid state tone decoders that act differently from the old mechanical reeds. Motorola made their solid state decoders to act like a old reed and still depend on that phase and timing.

Using a fast squelch circuit like in some fixed station equipment, along with the ANDing of the PL and the carrier squelch to open and the loss of either,OR, to close the audio gating in the receiver helps a lot to elimate the 'squelch crash'.

Belive me, I have had to a lot of changes 'screw arround' with decoders, especially in repeaters, to get rid of the 'crash'. My MICOR, MSF and MSR repeaters, and even a couple of old Regency repeaters do not crash (even with radios that have NO TX 'reverse burst' or carrier delay)..
I did some Master II repeaters also. Just adding a Com-Spec delay to the repeater transmitter drop-out helps.
bernie
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Post by bernie »

My two bits worth:
I suppose that this is not what you want to hear, but I have seen this before.

I tell the customer that it is a compatability issue. The squelch tail is heard because the manufacturer of what ever repeater you are using did not include the circuit necessary to eliminate the squelch tail.
What else is absent from your repeater?

Let the squelch tail remind you of how much was saved by going non-Motorola.
There is a very good reason why it works this way.
It allows the PL to control the receiver. The delay is to prevent "squelch flutter" on weak signals. The receiver is under control of the transmitter being received. This is one of the reasons that Motorola is so highly reguarded in the industry.

There are many manufacturers of after market boards that will immitate the real thing.

I have interfaced Micor encoder boards to many different stations.

The best solution is to replace the repeater with a Motorola, donate the old one to the ham club.
Aloha, Bernie
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c17loadsmasher
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Post by c17loadsmasher »

Tell the listeners/users to deal with it...especially if the system works, and works well. Seems like quite an investment to replace a repeater to get rid of a squelch tail...lol.
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N4DES
was KS4VT
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What radios do you own?: APX,XTS2500,XTL2500,XTL1500

Post by N4DES »

We used to use these by the box loads at Palm Beach Sheriff's office to give the Standard VHF GX3000's and HX400's Reverse Burst:

http://www.repeater-builder.com/com-spe ... 1-inst.gif

It worked ok operationally on a Motorola conventional back-bone, but was a little tight in the portable to install. The mobile was really easy to install.
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