[Elecraft] DMM recommendations

[Joe Subich, W4TV]

> When taking reflected power readings the slug should be 1/10 of the
> forward slug value when testing a reasonably good antenna. So, a 100
> watt forward slug would require a 10 watt reverse slug for reasonable
> accuracy.

Unfortunately, the smallest HF slug Bird make is 25 Watts.  That means
any SWR less than 1.4:1 (2.8% reflected power) is suspect with a 100 W
transmitter.  It is a shame that Bird do not offer a 10 (or 5 W HF
element) and the one reason I moved to the LP-100(A) several years ago.
However, I would never think to take the LP-100(A) or microHAM SMΩRF
out into the field.

73,

    ... Joe, W4TV


On 3/19/2018 8:10 PM, JOE wrote:
> I spoke to someone at Bird (when they were really Bird) years ago and I 
> was told that the Bird wattmeter is accurate to ±5% of top scale.  This 
> means that a 100 watt slug can be off ±5 watts _anywhere_ on the meter. 
> So, a transmitter emitting 50 watts out, using the Bird and a 100 watt 
> slug, can read between 45 and 55 watts.  That's why he said it was 
> important to keep the reading in the top 1/3 (highest) end of the 
> meter.  This is where the error is less.  When taking reflected power 
> readings the slug should be 1/10 of the forward slug value when testing 
> a reasonably good antenna.  So, a 100 watt forward slug would require a 
> 10 watt reverse slug for reasonable accuracy.
> 
> I retired my Bird 43 and the vast assortment of slugs for a Telewave 
> Model 44A wattmeter and never looked back.  The drawback to the 44A is 
> it is limited to 20-1000MHz.  The Bird would be good for HF use.
> 
> 73, Joe, K1ike
> 
> Date: Mon, 19 Mar 2018 18:40:41 +0000
>> Always bear in mind that their odd meters (30 uA) are very non-linear and
>> measurements made using element ranges that fall in the bottom 1/3 or 
>> so of
>> the scale are the most accurate.  Overall, they claim to be accurate 
>> to +/-
>> 20 percent of full scale.  HORRIBLE in
>> today's world!
>>
>> FWIW ...
>>
>> 73!
>>
>> K0PP
> 
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