Chuck, You are absolutely correct! However, the specific resistor value used for R405 in each MICOR station was deliberately selected to result in the desired deviation level. Thus, the R405 resistor value (nominally 33 kohms) varies from one station to the next. Note 409 on the schematic for the MICOR TLD5320A Exciter states that "R404 and R405 are factory selected so that Private Line deviation falls between 500 Hz and 1000 Hz limits."
The point I made was that Alinco, among many other manufacturers, simply used a certain value in almost every radio built, rather than a selected value, with the assumption that it would result in "enough" CTCSS deviation. As I pointed out, that value more often than not resulted in CTCSS deviation that was far above the appropriate or necessary level. However, as Bob points out, a very few Alinco models have CTCSS deviation adjustment pots, but those are the exception. Without exception, every Alinco radio I have tested- portable or mobile- has had CTCSS deviation above 1000 Hz. That is far too high, and it usually results in talk-off due to tone distortion. As others have noted, this issue of over-deviation of CTCSS tones is definitely not limited to Alinco, but is common practice in Amateur-grade radios. Lest others doubt the accuracy of my measurements, I should state that both of my service monitors have annual calibrations performed by the original vendors, with certifications traceable to the NIST. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Kelsey Sent: Thursday, March 15, 2007 3:45 AM To: [email protected] Subject: Re: [Repeater-Builder] Amateur-Grade Radios (Was: Fixed Audio) Commercial radios also used fixed values. The Micor is one example of fixed values for tone deviation. Chuck WB2EDV ----- Original Message ----- From: "Mike Morris WA6ILQ" <[EMAIL PROTECTED] <mailto:wa6ilq%40pacbell.net> > To: <[email protected] <mailto:Repeater-Builder%40yahoogroups.com> > Sent: Wednesday, March 14, 2007 11:37 PM Subject: Re: [Repeater-Builder] Amateur-Grade Radios (Was: Fixed Audio) > At 07:23 PM 03/14/07, Eric Lemmon WB6FLY wrote: >>Nate, >> >>Several years ago, I chastised ARRL Labs for failing to report the basic >>2-way radio performance parameters of 12dB SINAD sensitivity, voice >>deviation limit, CTCSS deviation limit, and center frequency accuracy. I >>did not get a satisfactory answer, but I suspect that there is a >>reluctance >>to disparage the performance of name-brand Ham radios. > > QST survives on the ads. The league doesn't want to risk the revenue. > As the wise man said, he who has the gold makes the rules. > >>Nearly every Amateur 2m radio I have tested has CTCSS deviation far in >>excess of the EIA/TIA recommended level of 750 Hz, and that level is not >>adjustable in most radios. > > Pots cost more than fixed resistors and that would reduce the profits.
