[Scan-DC] "Motorboating"?

[b_thom@juno.com]

On Fri, 01 Aug 2003 22:51:34 -0400 "Doug K." <oldsdoug@hotmail.com>
writes:
> All,
> 
> When listening to Montgomery Fire (I'm still listening on the VHF 
> patch), 
> will occasionally a "motorboating" sound (actually sounds like a 
> fire truck 
> engine idling!)... I know there was a post about this a few months 
> ago here, 
> but I'm sure I'll never find it!
>

It was from April. 

http://mailman.qth.net/pipermail/scan-dc/2003/020474.html
Motorboating on the Alexandria TRS

I said:

>>
A few months ago, there was a discussion here regarding motorboating
someone had heard while monitoring the Alexandria TRS. He might have had
a PRO-2067, and he wondered if there was a problem with his scanner.

On Friday night, while driving around seeing if the citizens of
Alexandria had thrown out anything good in their trash, I found a pair of
Koss TD/65 headphones. I had to dig extra hard too, as the headband had
become separated from the earpieces. Not only that, but it was raining. 

Today I tested them by plugging them into my recently purchased Bearcat
SC-180B, which, unlike my other scanners, has a stereo headphone jack. I
found that the headphones work perfectly well. Because the headphones
have better bass response than the itty-bitty speaker in the SC-180B, I
was able to hear for the first time the motorboating effect. It can be
heard in the background during the voice part of the transmission. When
the voice stops, the frequency of the motorboating increases to about
three times what it had been. This final burst at the higher frequency 
lasts for maybe a quarter-second before the transmission ceases entirely
and the squelch tail is heard.

I haven't tried Arlington's TRS to see if the motorboating is there as
well. As other listers wrote in at the time, the motorboating is part of
the Alexandria system and is not indicative of any problem with the
scanner.

HTH, as they say.
<<

Shawnerz said:

>>
Blair,
Like I said before, I'm pretty sure that's the 91 Hz
connect tone.  The tone at the end is a "signal" to
the receivers to mute.  That way there is no squelch
tail to the receiver that is expecting the "turn off
tone."
I'll have to poke around in the Motorola RSS.  There
are some confusing squelch/unsquelch/unmute/mute/And
unmute/And Unsqulech rules that can be established.
Perhaps someone else can explain them better.
-Shawn
<<

Search the archives for Shawnerz and his earlier comments on the subject.