[Amps] UHF Connectors

[Glen Zook]

It depends on the quality of the UHF series connectors as to how much loss.  A number of years ago, I had a client who decided to set up his own two-way radio test bench.  For some reason, he used PL-259 and PL-258 connectors from Radio Shack.  He also, for some unknown reason, had a total of 7-connectors in less than 10-feet of RG8/U plus a dummy load and a Bird 43 wattmeter.  

The first units he checked had a specified output of 35-watts in the 450 MHz to 470 MHz range.  He was reading well under 10-watts on his Bird 43.  The client telephoned me wanting to know why such a low reading.  I took my Bird 6154 dummy load / wattmeter with my coax jumper over to the client's office.  With the Bird 6154, the transmitters registered over 35-watts output.  Then, I used his cable, including all the Radio Shack connectors, to feed the 6154.  The power registered the same as with the client's wattmeter.

I started removing sections of jumper cable from the client's setup and the reading on the 6154 kept increasing.  Next, the jumper cable from the 6154 was used with the client's wattmeter.  A full 35-watts was read on his wattmeter.

Further examination showed right at a 1 dB loss in each of the Radio Shack connectors!  I did not check the connectors at lower frequencies.  The client replaced his jumper cables with a single piece of RG8/U with Amphenol PL-259 connectors at each end and his wattmeter read over 35-watts.

After that experience, I definitely avoid using Radio Shack connectors.  I don't know if the particular "batch" had problems or what.  But, the price of Radio Shack connectors usually is right at, and sometimes even more, than quality connectors.  As such, I don't take a chance and stay clear of Radio Shack where r.f. connectors are concerned.
 
Glen, K9STH


Website:  http://k9sth.com



On Tuesday, November 12, 2013 1:01 AM, Roger (K8RI) <k8ri at rogerhalstead.com> wrote:
 
On 11/11/2013 2:02 PM, Jim Brown wrote:
> On 11/11/2013 10:37 AM, Fuqua, Bill L wrote:
>> Isn't "UHF Connector" an oxymoron?


>
> The name dates from the '30s or early '40s.  No question that there's a
> small discontinuity due to the Zo of the connector, but it certainly
> doesn't matter below 50 MHz, and at higher frequencies is often swamped
> by line loss.
>

I have on average 10 connectors in line from the amp to the antennas. 
228 feet. With UHF type the additive loss is so small as measured on the 
VNA it's insignificant through 10 meters and only a slightky bit more on 
50 MHZ  I haven't checked 2-meters.

As the arrays for 144 and 440 are not going back up and the only VHF/UHF 
antennas will be Diamond duoband verticals Loss isn't much of a concern.
I leave the VNAs connected through a Delta-2 switch, so every tune up 
van have the characteristic traces overlain to see any differences. The 
sensitivity is good enough to see the effects of the wind on the 
antennas and trees.

After using a 4170C for about a year I added a second one to the second 
station.  They sure are different than the old MFJ.

73

Roger (K8RI)


> Several years ago, I made up a dozen or so lengths of coax for a DX trip
> using very low loss cable that I'd bought at a great price, surplus from
> a telecom bankruptcy -- construction much like LMR400, except #10 solid
> copper for the center, excellent braid/foil shield.  As a test, when I
> was finished, I connected them all in series, about 1,200 ft, and
> measured with HP generator and HP spectrum analyzer up to about 500 MHz.
> I had about 23 83-1SPs and 11 or 12 barrels in line. The loss at 500 MHz
> was less than the published spec for the cable. Loss was measured by
> substitution (that is, differencing a short direct connection between
> generator analyzer with the cable under test) at all of the test
> frequencies.
>
> 73, Jim K9YC
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> Amps at contesting.com
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>


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