[Elecraft] Mic Gain Changing

[Jack Smith]

Don:

I've purchased several surplus 75 watt high quality terminations from 
Ridge Equipment. These are cell site pulls, and are flat from DC up to 1 
GHz plus and sell for $11.95. For a small amount more, Ridge will give 
you a return loss sweep.

https://www.ridgeequipment.com/store/dummyloads.html is  the URL for 
their loads page. Sometimes they will have Decibel Products 100 watt 
loads that, for ham purposes, are really 150 or 200 watt loads, but I 
don't see any listed at the moment. The 75 watt loads are OK at 75 watts 
but I would not push them past 100 or so watts for long periods.

As I say, I have a couple of these and recommend them. Sure a lot better 
than the Heath Cantenna I built 40 years ago--and they don't leak.

Jack K8ZOA


Don Wilhelm wrote:
> Steve,
>
> Your "confession" should be preserved in bold type for others to heed 
> and lessons to be learned.
>
> Attempting to do calibrations with 'almost good enough' dummy loads (or 
> other equipment too) will result in 'funny behavior' - one cannot obtain 
> precision results with 'almost good enough' equipment.
>
> An accurate dummy load is the basis for many amateur measurements and 
> calibrations.  1% 50 ohm dummy loads are not difficult to come by.  A 
> 100 watt dummy load can be built from a thick film power resistor 
> (Caddock MP9100-50), a heat sink and a BNC, UHF, or N connector.  These 
> 50 ohm 1% resistors, when mounted on a heat sink with zero length leads 
> to the connector, will be flat up to 200 MHz or more depending on the 
> construction techniques.  That kind of dummy load and a precision 
> voltage reference (along with some basic math) have become the basis for 
> calibrating other equipment on my workbench.  I practice the "trust no 
> measurement tool until it has proven its accuracy" rule.
>
> Good calibrated equipment does not need to be expensive, nor of 
> laboratory quality, but it must be used intelligently with respect for 
> its shortcomings.
>
> 73,
> Don W3FPR
>
>
> list1 wrote:
>   
>> Hi Everyone,
>>
>> OK I seemed to have "removed" the problem.
>>
>> I added 11 small resistors in parallel to my MFJ 949E dummy load to change
>> its resistance from about 56.5 Ohms to close to 50.0 Ohms.  I then ran the
>> "Calibrate Transmitter Gain" procedure from the configuration Menu of the K3
>> utility.  Now I can talk with 100 Watts and 6 bars of ALC all the time
>> regardless of the temperature of the radio.  No more fiddling with the Mic
>> gain.  Changing the Mic gain affects the power out and ALC reading now as
>> expected.
>>
>> I think when I built my K3 I skipped the "TX Gain Calibration" step.  I may
>> have thought that it was optional like the Wattmeter calibration, but with
>> my dummy load being off I think I was afraid that I would do more harm then
>> good.
>>
>> I can now see how some people have problems with the K3 by not following
>> instructions.  I am a bit amazed the radio worked as well as it did in spite
>> of the "loose nut in operator's chair" syndrome I was experiencing.
>>
>> OK, now to have even more fun with the radio, now that is it perfect.
>>
>> Steve, W2MY
>>
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