Originally I requested a source for various length of cables with SMA Male
on one end to plug into a HT (Kenwood TH-F6A) and the other end a PL-259.
Lengthy and comprehensive treads soon made me realize that the PL-259 would
be ill advised especially at UHF & higher. So I found some ready made cables
with SMA and N connectors. The only problem (if it's really a problem) is
those skinny cables they come in. Some claim that they are 50 ohms, another
RG-174. I don't know the other types. Do you think it will be alright to use
those narrow cables from my HT to an amplifier to my monitoring meter and
then use regular RG 8 to the base antenna? Will those skinny cables present
some kind of mismatch. You know it's almost impossible to solder a SMA
connector to an RG 8. Thoughts, please? Thank you.

Cordially,
west
AF4GC

In article ,
west wrote:

Originally I requested a source for various length of cables with SMA Male
on one end to plug into a HT (Kenwood TH-F6A) and the other end a PL-259.
Lengthy and comprehensive treads soon made me realize that the PL-259 would
be ill advised especially at UHF & higher. So I found some ready made cables
with SMA and N connectors. The only problem (if it's really a problem) is
those skinny cables they come in. Some claim that they are 50 ohms, another
RG-174.

RG-174 is a 50-ohm cable, just over 1/10" in diameter. It's a decent
choice for HT-to-whatever pigtails, at long as the length isn't so
great that losses become unacceptable.

I don't know the other types. Do you think it will be alright to use
those narrow cables from my HT to an amplifier to my monitoring meter and
then use regular RG 8 to the base antenna?

Almost certainly for short lengths. I wouldn't use it for long runs.

The attenuation per 100' of RG-174 is around 13 dB at 146 MHz, and
about twice that at 440. Thus, at 440, 10' of the cable would lose
you around 2.5 dB, or less than 1/2 of an S-unit at the conventional
calibration. This loss would occur for both transmission and reception.

There are other cables of this size which are less lossy - LMR-100A
has approximately half as much signal loss per foot.

Both RG-174 and LMR-100A have solid center conductors, and might not
stand up to a very large number of flexing cycles. A cable of similar
size with a multistrand center conductor might live longer.

Will those skinny cables present
some kind of mismatch.

Not unless the manufacture is seriously botched (e.g. cable not
soldered to connector correctly). They're the same impedance as RG-8,
but are a lot more lossy.

You know it's almost impossible to solder a SMA
connector to an RG 8. Thoughts, please? Thank you.

Go for it. A pigtail of anywhere from 18" to a few feet should act as
a perfectly acceptable strain-relief for your HT's SMA connector, and
even at 440 its loss should be low enough that you'd be unlikely to
notice it.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

So long as your runs are short, there should be no problem. I assume
your HT expects to see something reasonably close to a 50 ohm load, and
using 50 ohm coax for your connections makes perfect sense in that
case. Small coax in general has higher loss than large coax. For a
100 foot run, that might be a problem. For RG-174-type cable at about
25dB per 100 feet at 450MHz, 100 feet would be pretty awful. But four
feet is about 1dB, which you might notice but would be a fraction of
the contribution of, say, 100 feet of RG-8-type cable at maybe 4dB.
So, how long a "skinny cable" are you thinking of, and how long is your
RG-8 run in comparison?

Cheers,
Tom

You know it's almost impossible to solder a SMA connector to
an RG 8. Thoughts, please? Thank you.

Cordially,
west
AF4GC

I found on Ebay reasonable priced SMA to N adapters. Might
save you from mounting a small connector on a thick cable!

sam

On Thu, 09 Mar 2006 00:04:53 GMT, "west"
wrote:

Originally I requested a source for various length of cables with SMA Male
on one end to plug into a HT (Kenwood TH-F6A) and the other end a PL-259.
Lengthy and comprehensive treads soon made me realize that the PL-259 would
be ill advised especially at UHF & higher. So I found some ready made cables
with SMA and N connectors. The only problem (if it's really a problem) is
those skinny cables they come in. Some claim that they are 50 ohms, another
RG-174. I don't know the other types. Do you think it will be alright to use
those narrow cables from my HT to an amplifier to my monitoring meter and
then use regular RG 8 to the base antenna? Will those skinny cables present
some kind of mismatch. You know it's almost impossible to solder a SMA
connector to an RG 8. Thoughts, please? Thank you.

West,

I would be thinking about a tail made from LMR-195. It is a low loss
cable, dimesionally compatible with RG58 connectors. One meter of it
has a loss of 0.25dB at 440MHz.

Nobody solders these things do they? Get a hold of crimp UHF and SMA
connectors suitable for RG58 and borrow a crimp tool to make them up.
Might be worth buying a couple of strain relief boots as well.

Alternatively, get a bit of old cellular cable, but it may have a
solid centre conductor... check it out.

Keep in mind that a run of 30m of RG8 has a loss close to 5dB at
440MHz, ie only 30% of the transmitter power reaches the feedpoint.

Owen
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