Re: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-22 Thread Jim B.
skipp025 wrote:

> I'm heading toward the question of "is it better to reduce 
> or remove (mute) the ctcss after the phase shift or just 
> not worry about it?".  As mentioned in one reply... there 
> might be enough time for some fast decoders to "re-lock" on 
> the inverted ctcss before the tx drops.  200 mS might not 
> be much time but... is/does it possibly confuse some of the 
> reverse burst ctcss decoders? 
> 

It does vary quite a bit. I've seen some that close so fast that most 
radios will open it back up again, and others that close so slow that 
most radios go away before it closes.

I think a good value to use would be 160-180 mS-my opinion...
-- 
Jim Barbour
WD8CHL



Re: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-22 Thread Jim B.
[EMAIL PROTECTED] wrote:

> There is no 'reverse burst decoder' per se in a tone decoder - it is 
> just driven with the out of phase energy long enough to cause it to 
> close very quickly. All tone decoders react to the reverse burst, not 
> just one that is specially configured to react to a reverse burst. I 
> don't know of any special circuitry in a tone decoder that makes it 
> more susceptible to a reverse burst than a normal tone decoder.
> 
> 73 - Jim W5ZIT

The cheaper decoders that don't have good 'talk-off' immunity will have 
a delay cap in the output to keep it open for a period of time no matter 
what. Some of them are so long that even 'chicken-burst' won't work. 
Even the early TS-32's were like that.

Many newer 'decoders' are actually in software/firmware in the radio, 
and sense the phase inversion in S/W.

In fact, many new radios do everything in S/W except the actual RF 
filtering and amplification. Feed the high-IF in one pin, get audio out 
another.
-- 
Jim Barbour
WD8CHL



Re: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-21 Thread no6b
At 1/19/2007 18:25, you wrote:
>Actually, the electronic CTCSS decoders react about the same as the old
>reeds. The physics of the matter causes the filters that can discern
>for instance - 100 Hz from 97 Hz or 103 Hz to be very narrow, and they
>ring - even when the driving tone is removed. By reversing the tone
>phase for a short period of time, the energy in the filter is driven to
>zero very quickly, and if the tone is removed from the decoder input at
>the right time, the tone decoder closes very quickly, and you get very
>short squelch bursts at the end of a transmission.

I was never able to get a ComSpec TS-32 decoder to respond to reverse burst 
of any kind.

Bob NO6B




[Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-19 Thread skipp025
I believe the cap you speak of is to delay the transmitter 
on/keyed for an additional time, which the mfgr specs at 
200mS (milli seconds).  Removing or lowering the cap value 
would reduce the delayed ptt time. 

The focus of my post is to ask people how their true reverse 
burst decoders respond to the time from the reverse burst 
phase inverter until the delayed ptt drops the transmitter. 

For some x-value of time the ctcss decoder receives the 
phase shifted ctcss, which remains on constant until the 
tx drops. I'm interested to know how the various decoders 
handle short reverse burst "inverted" tone.  

I'm heading toward the question of "is it better to reduce 
or remove (mute) the ctcss after the phase shift or just 
not worry about it?".  As mentioned in one reply... there 
might be enough time for some fast decoders to "re-lock" on 
the inverted ctcss before the tx drops.  200 mS might not 
be much time but... is/does it possibly confuse some of the 
reverse burst ctcss decoders? 

thanks so far for your replies...  keep them coming. 

cheers, 
skipp 

> I played around with using the RB-1 board on my repeater 
> transmitters using motorola and several other receivers in 
> tone squelch.  Eventually I found it was better to remove 
> the capacitor which causes the RB-1 to send NO tone for
> the last 100ms (or what ever the timing is). 
> 



Re: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-19 Thread w5zit
Actually, the electronic CTCSS decoders react about the same as the old 
reeds. The physics of the matter causes the filters that can discern 
for instance - 100 Hz from 97 Hz or 103 Hz to be very narrow, and they 
ring - even when the driving tone is removed. By reversing the tone 
phase for a short period of time, the energy in the filter is driven to 
zero very quickly, and if the tone is removed from the decoder input at 
the right time, the tone decoder closes very quickly, and you get very 
short squelch bursts at the end of a transmission.

There is no 'reverse burst decoder' per se in a tone decoder - it is 
just driven with the out of phase energy long enough to cause it to 
close very quickly. All tone decoders react to the reverse burst, not 
just one that is specially configured to react to a reverse burst. I 
don't know of any special circuitry in a tone decoder that makes it 
more susceptible to a reverse burst than a normal tone decoder.

73 - Jim W5ZIT

-Original Message-
From: [EMAIL PROTECTED]
To: Repeater-Builder@yahoogroups.com
Sent: Fri, 19 Jan 2007 2:27 PM
Subject: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

--- In Repeater-Builder@yahoogroups.com, "skipp025" <[EMAIL PROTECTED]>
wrote:
>
> Re: Reverse Burst Comments (Com Spec RB-1)
>
> If you add a circuit like the Com Spec RB-1 board to the typical
> repeater system using a ts-32/ts-54 board... the tx ctcss is not
> disabled or removed before the RB-1 delayed ptt line drops.
>
> So you have the phase inverted ctcss present for at most up to
> 200 ms typical before the tx drop. If you don't remove the ctcss
> source the inverted ctcss remains up until the tx off/drop...
>
> Any of you actually running the RB-1 board with a true reverse
> burst type ctcss decoder (built into your radio)? Is a true
> reverse burst decoder in your commercial radio completely "fooled"
> by the phase inverted ctcss before carrier drop function.
>
> Or do you actually still hear some minor difference from the
> rb-1 type operation vs an original true Motorhead (Motorola)
> encoder - decoder operation?
>
> Thinking out-loud about having to possibly mute the ctcss at some
> time after invert and before the delayed ptt drop as a requirement
> to get the full/true reverse burst quiet squelch close.
>
> Any of you been down that road already?
>
> skipp
>
Skipp,
I find your comments interesting in that the purpose that Motorola
had in using "reverse burst" of the PL tone was to quickly damp the
mechanical reed in the PL decoder to close the squelch and eliminate
the user from hearing the noise burst. But of course you knew that.
However, in later model radios there is no mechanical vibrating reed
to abruptly dampen and stop the vibrating from being detected. So
where is the need for a inverted burst if there are no receivers
using mechanical reeds as PL tone decoders?
Incidently Motorola did not use an inverted reverse burst of 180
degrees. Their designs used 270 degrees since the PL reed then
stopped vibrating faster and the amplitude of the burst was also
increased to hasten the reed to stop.
Don't modern day receivers use electronic circuitry to detect PL
tones, and aren't the detectors not using a ringing decoder? If so
isn't the purpose of having a "reverse burst" unnecessary?
I can remember many years ago that some hams used a circuit which
they refered to as "polish PL" which turned off the PL tone before
the xmtr dropped and had no "reverse burst". It seems like I'm
hearing more of the same.
Where am I going wrong here?
Allan Crites

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Re: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-19 Thread JOHN MACKEY
I played around with using the RB-1 board on my repeater transmitters using
motorola and several other receivers in tone squelch.  Eventually I found it
was better to remove the capacitor which causes the RB-1 to send NO tone for
the last 100ms (or what ever the timing is).


--- In Repeater-Builder@yahoogroups.com, "skipp025" <[EMAIL PROTECTED]> 
wrote:
SNIP
> Any of you actually running the RB-1 board with a true reverse 
> burst type ctcss decoder (built into your radio)? Is a true 
> reverse burst decoder in your commercial radio completely "fooled" 
> by the phase inverted ctcss before carrier drop function. 
> 
> Or do you actually still hear some minor difference from the 
> rb-1 type operation vs an original true Motorhead (Motorola) 
> encoder - decoder operation? 
> 
> Thinking out-loud about having to possibly mute the ctcss at some 
> time after invert and before the delayed ptt drop as a requirement 
> to get the full/true reverse burst quiet squelch close. 
> 
> Any of you been down that road already? 




RE: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-19 Thread Jeff DePolo

> Skipp,
> I find your comments interesting in that the purpose that Motorola
> had in using "reverse burst" of the PL tone was to quickly damp the 
> mechanical reed in the PL decoder to close the squelch and eliminate 
> the user from hearing the noise burst. But of course you knew that. 
> However, in later model radios there is no mechanical vibrating reed 
> to abruptly dampen and stop the vibrating from being detected. So 
> where is the need for a inverted burst if there are no receivers 
> using mechanical reeds as PL tone decoders?

Because the software-based decoders respond the same way as a mechanical
reed to the reverse burst.  When the phase shift occurs, the correlation
routines "lose lock" causing the processor to signal the audio gates to
close.  Eventually the software routine would regain lock at the new
phase, but the transmitter drops before that can happen.

Hardware-based designs that don't look for change of phase but rather
just the presence or absence of tone are another story, but fortunately
those aren't very common nowadays.  Some of the early non-reed
non-software decoders used what were basically very narrow bandpass
filters followed by a detector.  They could care less what the phase of
the incoming tone was as long as the frequency was right - you always
heard the squelch crash when the transmitter unkeyed.  "Chicken burst",
or transmitting no PL before transmitter drop, was invented as a means
of getting those types of decoders to mute before the transmitter
dropped.

> I can remember many years ago that some hams used a circuit which
> they refered to as "polish PL" which turned off the PL tone before 
> the xmtr dropped and had no "reverse burst". 

Yeah, "chicken burst", same thing.

--- Jeff

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Re: [Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-19 Thread Jim B.
wa9zzu wrote:
> --- In Repeater-Builder@yahoogroups.com, "skipp025" <[EMAIL PROTECTED]> 
> wrote:
>> Re: Reverse Burst Comments (Com Spec RB-1) 
>>
>> If you add a circuit like the Com Spec RB-1 board to the typical 
>> repeater system using a ts-32/ts-54 board... the tx ctcss is not 
>> disabled or removed before the RB-1 delayed ptt line drops. 
>>
>> So you have the phase inverted ctcss present for at most up to 
>> 200 ms typical before the tx drop.  If you don't remove the ctcss 
>> source the inverted ctcss remains up until the tx off/drop... 
>>
>> Any of you actually running the RB-1 board with a true reverse 
>> burst type ctcss decoder (built into your radio)? Is a true 
>> reverse burst decoder in your commercial radio completely "fooled" 
>> by the phase inverted ctcss before carrier drop function. 
>>
>> Or do you actually still hear some minor difference from the 
>> rb-1 type operation vs an original true Motorhead (Motorola) 
>> encoder - decoder operation? 
>>
>> Thinking out-loud about having to possibly mute the ctcss at some 
>> time after invert and before the delayed ptt drop as a requirement 
>> to get the full/true reverse burst quiet squelch close. 
>>
>> Any of you been down that road already? 
>>
>> skipp
>>
> Skipp,
> I find your comments interesting in that the purpose that Motorola 
> had in using "reverse burst" of the PL tone was to quickly damp the 
> mechanical reed in the PL decoder to close the squelch and eliminate 
> the user from hearing the noise burst. But of course you knew that. 
> However, in later model radios there is no mechanical vibrating reed 
> to abruptly dampen and stop the vibrating from being detected. So 
> where is the need for a inverted burst if there are no receivers 
> using mechanical reeds as PL tone decoders?
> Incidently Motorola did not use an inverted reverse burst of 180 
> degrees. Their designs used 270 degrees since the PL reed then 
> stopped vibrating faster and the amplitude of the burst was also 
> increased to hasten the reed to stop.
> Don't modern day receivers use electronic circuitry to detect PL 
> tones, and aren't the detectors not using a ringing decoder? If so 
> isn't the purpose of having a "reverse burst" unnecessary?
> I can remember many years ago that some hams used a circuit which 
> they refered to as "polish PL" which turned off the PL tone before 
> the xmtr dropped and had no "reverse burst". It seems like I'm 
> hearing more of the same.
> Where am I going wrong here?
> Allan Crites

The problem with just turning the tone off is that most all decoders 
take a MUCH longer time to just coast to a stop, rather then be told 
'I'm about to go off the air, close now'.

Digital squelch (CDCSS, or DPL in Motorola terms, DCG for GE folks) 
sends a short burst of 133hz tone for the same purpose-to let the 
decoder know that the transmission is over and to close.

And everything I saw had Motorola's original R/B at 120 degrees, not 270.

But as someone wise once said, "I could be wrong."
-- 
Jim Barbour
WD8CHL



[Repeater-Builder] Re: Reverse Burst Comments (Com Spec RB-1)

2007-01-19 Thread wa9zzu
--- In Repeater-Builder@yahoogroups.com, "skipp025" <[EMAIL PROTECTED]> 
wrote:
>
> Re: Reverse Burst Comments (Com Spec RB-1) 
> 
> If you add a circuit like the Com Spec RB-1 board to the typical 
> repeater system using a ts-32/ts-54 board... the tx ctcss is not 
> disabled or removed before the RB-1 delayed ptt line drops. 
> 
> So you have the phase inverted ctcss present for at most up to 
> 200 ms typical before the tx drop.  If you don't remove the ctcss 
> source the inverted ctcss remains up until the tx off/drop... 
> 
> Any of you actually running the RB-1 board with a true reverse 
> burst type ctcss decoder (built into your radio)? Is a true 
> reverse burst decoder in your commercial radio completely "fooled" 
> by the phase inverted ctcss before carrier drop function. 
> 
> Or do you actually still hear some minor difference from the 
> rb-1 type operation vs an original true Motorhead (Motorola) 
> encoder - decoder operation? 
> 
> Thinking out-loud about having to possibly mute the ctcss at some 
> time after invert and before the delayed ptt drop as a requirement 
> to get the full/true reverse burst quiet squelch close. 
> 
> Any of you been down that road already? 
> 
> skipp
>
Skipp,
I find your comments interesting in that the purpose that Motorola 
had in using "reverse burst" of the PL tone was to quickly damp the 
mechanical reed in the PL decoder to close the squelch and eliminate 
the user from hearing the noise burst. But of course you knew that. 
However, in later model radios there is no mechanical vibrating reed 
to abruptly dampen and stop the vibrating from being detected. So 
where is the need for a inverted burst if there are no receivers 
using mechanical reeds as PL tone decoders?
Incidently Motorola did not use an inverted reverse burst of 180 
degrees. Their designs used 270 degrees since the PL reed then 
stopped vibrating faster and the amplitude of the burst was also 
increased to hasten the reed to stop.
Don't modern day receivers use electronic circuitry to detect PL 
tones, and aren't the detectors not using a ringing decoder? If so 
isn't the purpose of having a "reverse burst" unnecessary?
I can remember many years ago that some hams used a circuit which 
they refered to as "polish PL" which turned off the PL tone before 
the xmtr dropped and had no "reverse burst". It seems like I'm 
hearing more of the same.
Where am I going wrong here?
Allan Crites