[Elecraft] UHF connectors [was: Array Solutions Lightning Arrestor]

[Bob McGraw K4TAX]

I concur with Jim's comments on loss.   I view one should always look at 
the component which contributes the greatest loss in the system,  that 
is most often the feedline.  One should strive to improve the condition 
by using a line type of less loss.  {i.e. better quality feed line} and 
eliminate excessive feed line lengths.    Factors influencing line  
losses are; type of line, age of the line, length of line, frequency and 
reflected power. Manufactures produce charts and tables showing loss of 
a specific type of line taking into consideration of length and 
frequency. These numbers are for new or known good line and not likely 
"hamfest" bargain line.

A second component which often contributes significant loss is the all 
famous "antenna tuner".    Recent tests show some tuners, under some 
load conditions can contribute up to 25% of added loss or more.   And 
while at the same time, the loss in the feedline remains the same.

This brings me to the point where I view many hams obsess over SWR 
values.  Unless the transmitter is folding back power, as many 
un-necessarily do, then the use of the ATU may benefit making the 
transmitter happy, but at the sacrifice of added loss to the system.  To 
that end, there are several brands and models of radios, past and 
present, that do not fold back power with reasonable SWR values.  I find 
it not at all uncommon to operate with a 3:1 SWR without issues.  In 
this configuration, adding the ATU makes the SWR to the radio look 
better, but adds loss induced by the tuner and does not change the loss 
in the feed line.

There is an interesting compilation of data on various match boxes i.e. 
ATU's  and their performance found on the following link.   The compiled 
information and data is from various sources and presented in XLS format.

http://www.dj0ip.de/antenna-matchboxes/matchbox-shoot-out/

73

Bob, K4TAX




On 2/11/2018 10:25 PM, Jim Brown wrote:
> Thanks for this excellent post, Alan! IMO, "mismatch loss" is a 
> figment of the imagination of those who never get outside the lab. 
> Transmission lines was one of my favorite EE courses, and I never 
> heard of it until I heard it referenced in online discussions a few 
> years ago. And the purported losses in connectors are an urban legend 
> with almost basis in fact. Several years ago, W8JI poetically observed 
> that if the 1 dB loss falsely attributed to UHF connectors was true, 
> each would be burning 35 W carrying a legal limit signal, and be 
> starting fires!
>
> Keeping track of losses in systems is, of course, a great thing. Our 
> FD group runs (and has won several times) FD 1A QRP Battery. Every 
> piece of coax in our station is low loss RG8 or RG11.
>
> 73, Jim K9YC
>
> On 2/11/2018 8:03 PM, Alan wrote:
>> Hi Al,
>>
>> Yes, but don't forget that the connector "loss" is a mismatch loss, 
>> not absorptive power loss.  In other words, it affects the SWR 
>> slightly but does not actually absorb any power.
>>
>> If you are using any kind of antenna tuner and tuning for 1:1 SWR, 
>> mismatch "losses" have no effect.  Even if you aren't doing that, the 
>> antenna is probably not a perfect 50-ohm resistive load anyway, so 
>> the connectors' mismatches are about as likely to make the SWR better 
>> as worse, depending on the phase and magnitude.
>>
>> But the general point is sound.  Power loss is even more important 
>> for QRP than for QRO even though the  number of watts of loss is 
>> less.  When the other station can barely hear you, every dB counts!
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