[AMRadio] AM Bandwidth and Audio Quality (was, > SourceBroadcastXmtrs)

[John Lyles]

I used to calibrate TCTs and TCAs at Delta Electronics in VA when I 
worked for them before 1980. The basic toroidal current transformer 
begins to exhibit strays that cause accuracy degradation above 2 MHz. I 
know this because I tried to operate one at 2800 KHz in 1998, to measure 
40 Amps of RF. They were not accurate and the guys at Delta didn't make 
any promises. Pearson current transformers, on the other hand, come in a 
variety of sizes and current ratings, and go far into the MHz. Problem 
is the cost, but maybe used ones pop up on epay. I use them extensively 
to measure pulsed (not DC) currents and RF on large tetrode amplifiers.

Hewlett Packard power meters like the old HP436, 437 and 438 series can 
be found online used, but you need a mating power detector head. With a 
known power attenuator (now you need a network analyzer!) you can get 
very accurate carrier measurements. There just isn't  a free lunch with 
regard to measuring Rf power accurately. Simple thermocouple ammeters 
and known resistances seem to be the easiest.
John
K5PRO

> -----Original Message-----
> From: BILL GUYGER
> Sent: Tuesday, June 21, 2011 8:32 PM
> To: Discussion of AM Radio in the Amateur Service
> Subject: Re: [AMRadio] AM Bandwidth and Audio Quality (was
> SourceBroadcastXmtrs)
>
> Delta is REAL proud of their equipment so I doubt there are going to be many
> spares laying around. I just replaced 4 20 Amp. max Toroid + meter combos at
> KTCK with ones rated for 40 A. The old ones will be kept for spares for KLIF
> or
> sent to other stations within the company that might need a replacement. Not
> saying "it ain't gonna happen" just don't hold your breath.
>
>
> In addition, Delta generally only guarantees them up to 2 Mc.  They'll
> probably
> be fiarly accurate thru 80 M. but ????
>
> Bill AD5OL
**
>