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M0PZT > FT817 28.04.07 13:09l 41 Lines 1856 Bytes #999 (0) @ WW
BID : 287_M0PZT
Read: GUEST DL1RX VE7HFY DG4IAK
Subj: Re: Max current from mic 5v pi
Path: DB0FHN<DB0MRW<DK0WUE<DB0RES<ON0AR<GB7CIP<GB7TUT<GB7ESX<GB7ESX
Sent: 070428/1120 @:GB7ESX.#31.GBR.EU $:287_M0PZT Sally 4.1.223 Chelmsford, Ess
Date: Sat, 28 Apr 2007 11:20:30
From: M0PZT@GB7ESX.#31.GBR.EU (Charlie)
To: FT817@WW
Subject: Re: Max current from mic 5v pi
Andy G0FTD wrote:
> These days broadcasters (cue M0PZT) use Optimod units to introduce
> *selected* harmonic distortions to create a modulation
> "reinforcement" effect.
>
> You get AM and FM versions to create the correct "timbre" - which is
> really what the subtle distortions are nostalgically referred to.
Optimod is certainly the most popular brand - Correct, there are AM+FM versions which specifically cater for the frequency
response of those transmission methods. I've no experience with AM Optimods, but from what I've heard - They are generally
set to create a loud punchy sound because many schools of thought tend to go with "the loudest is the best and gets more
listeners". Usually, the opposite is true.
Signal chain is typically:
SOURCE - FILTER - AGC - MULTIBAND - LIMITER - TX
It's possible to make a home-brew NE5534 limiter sound better than a 5k Optimod - Adjustment, listening, and more adjustment
is critical. The nicest and most pleasing sound is the one that people will choose.
But going back to your original point, Andy - I think you need to be careful about how much gain and limiting you put on your
mic. It's all very well being loud and punchy, but you don't want next door's lawmower as part of the QSO or the seagulls
down the beach squawking their CQ calls.
On a related note, I think I'm also about due for another rant about HF operators who insist on paying daft amounts of money
for "studio" microphones that boast a 20Hz-20KHz frequency range... Yes, I'm sure they sound great through a hi-fi, but
remind me, what's the bandwidth of an HF AM or SSB signal again ?!
--
Charlie - M0PZT @ GB7ESX.#31.GBR.EU
MB7ICF-L 6m+70cm EchoLink Gateway
http://www.m0pzt.com
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