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

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alorona

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

Excellent. Thank you, Alan. Data for this particular measurement are very difficult to find on the web -- of course it took an ex-HP guy to do it!

Times Microwave (a manufacturer of coaxial cable) says 0.01 dB per UHF connector pair (PL-259-to-SO-239) at HF; I have seen other private measurements that estimate 0.02 dB; and now this data from N1AL. I usually take the greater of these, 0.02 dB, as a worst-case number. But Alan's measurements pretty much show that the loss at HF is almost too small to measure-- even if he had performed a full two-port cal.

Even so, you might be surprised to see how quickly it can add up. Beginning at the transmitter output (or receiver input) it is not uncommon to find 20 or more UHF connections in the path to the antenna. Using the 0.02 dB worst-case figure, that's at least 0.4 dB, or 9% of your power. I wouldn't worry about that but I know there are folks on here that would be bothered by that.

This, of course, is not counting loss in cables, filters, lightning arrestors, power meters, bulkheads, switches, antenna tuners, baluns, amplifier through-paths, transmission lines, etc. These can add another dB or more to the total and far outweigh any loss in UHF connectors. If you want to minimize losses, UHF connectors are the last thing you should worry about.

I encourage you to do an analysis to determine your system efficiency. I recently did so and discovered that I have a worst-case loss (to the feedpoint up at the antenna) of 1 dB, which is 21% of my power. Gone. Forever. Whoosh!

Al W6LX

_______________________________________________________

--------- Type N -------- ---------- UHF ----------

FREQ (MHz) TOTAL LOSS PER CONNECTOR TOTAL LOSS PER CONNECTOR

1.8 0 dB 0 dB 0 dB 0 dB

30 0 0 0 0
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Bill Frantz

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

The losses pile up for those running QRP or QRPP. I have
frequently thought that a QRP system which has the final
amplifier at the feed point of the antenna would be very attractive.

A crude way of accomplishing a feed point amp would be to take a
radio like the Rockmite and place it at the feed point. If you
run the Rockmite with a 9V battery, all you just need wires for
the paddle and the headphones.

The big problem as I see it is weight at the feed point. In
theory, you could handle the whole operation with a RG-174 feed
line. Run DC power on the feed line, and have the feedpoint
electronics switch between transmit and receive depending on the
signal level on the coax.

But this is just another of the projects lined up to fill the
time when I'm not operating.

73 Bill AE6JV

On 2/11/18 at 11:49 AM, [hidden email] (Al Lorona) wrote:

>I encourage you to do an analysis to determine your system
>efficiency. I recently did so and discovered that I have a
>worst-case loss (to the feedpoint up at the antenna) of 1 dB,
>which is 21% of my power. Gone. Forever. Whoosh!

---------------------------------------------------------------------------
Bill Frantz | Re: Computer reliability, performance, and security:
408-356-8506 | The guy who *is* wearing a parachute is
*not* the
www.pwpconsult.com | first to reach the ground. - Terence Kelly

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Alan Bloom

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

In reply to this post by alorona

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!

Alan

On 02/11/2018 11:49 AM, Al Lorona wrote:

> Excellent. Thank you, Alan. Data for this particular measurement are very difficult to find on the web -- of course it took an ex-HP guy to do it!
>
> Times Microwave (a manufacturer of coaxial cable) says 0.01 dB per UHF connector pair (PL-259-to-SO-239) at HF; I have seen other private measurements that estimate 0.02 dB; and now this data from N1AL. I usually take the greater of these, 0.02 dB, as a worst-case number. But Alan's measurements pretty much show that the loss at HF is almost too small to measure-- even if he had performed a full two-port cal.
>
> Even so, you might be surprised to see how quickly it can add up. Beginning at the transmitter output (or receiver input) it is not uncommon to find 20 or more UHF connections in the path to the antenna. Using the 0.02 dB worst-case figure, that's at least 0.4 dB, or 9% of your power. I wouldn't worry about that but I know there are folks on here that would be bothered by that.
>
> This, of course, is not counting loss in cables, filters, lightning arrestors, power meters, bulkheads, switches, antenna tuners, baluns, amplifier through-paths, transmission lines, etc. These can add another dB or more to the total and far outweigh any loss in UHF connectors. If you want to minimize losses, UHF connectors are the last thing you should worry about.
>
> I encourage you to do an analysis to determine your system efficiency. I recently did so and discovered that I have a worst-case loss (to the feedpoint up at the antenna) of 1 dB, which is 21% of my power. Gone. Forever. Whoosh!
>
>
> Al W6LX
>

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Jim Brown-10

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

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!

Bob McGraw - K4TAX

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

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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Edward R Cole

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

In reply to this post by alorona

In fact my N-connector at my in-line Bird Meter element does get warm
enough at 1500w at 144-MHz to "barely" discern by touch. Since room
temp (70F) is 17c the connector may be at about 25c (nothing to write
home about).

When I first began operation of my 2m-8877 above 1kW it did burn up a
N-connector which probably had poor connection. It was an old run of
RG213 which should have been replaced for running that level. I
replaced the two sections of coax with a single 20-foot run of
LMR-600 which dissipates 0.216 dB which at 1500w is 73w power
loss). LMR-600 at 150-MHz is rated at 1.08 dB loss/100-foot.

So I run the amp with 1400w indicated by power meter which implies
the amp is outputing 1500w (nom.). Most of the time I run 1300w
which allows for 5% calib. error in the Bird indication.

In the effort to achieve best NF at 1296, I actually measured
connector loss in an N-elbow. It was below my measurement resolution
of 0.02 dB. How I measured loss was by reading thermal noise from a
50-ohm termination with my SDR-IQ with sw set or 0.02-dB/DIV
display. I only began to see some loss when I connected N-elbow +
N-relay + N/sma adapter. That measured 0.15 dB at
1296-MHz. Interestingly 0.1 dB was contributed by just the N/sma adapter.

For use below 50-MHz connector loss is negligible. Cable loss is way
more significant but only above 50-MHz. Of course that is for NEW
cable. That 25-year old run of RG8 might be loosing 2-3 dB at
20m. Cables do not last forever! Hint: measure them to know.

73, Ed - KL7UW

From: Jim Brown <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] UHF connectors [was: Array Solutions Lightning
Arrestor]

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

73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
[hidden email]

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alorona

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

In reply to this post by Alan Bloom

Hi,

Okay, I thought your measurements were like S21 and could be considered a
transmission (thru) loss. The other measurements I referred to were -- in
other words, I don't believe they were measurements of 'mismatch loss'. The
Times Microwave loss figure was definitely a transmission loss.

I think it's clear that UHF connectors, at HF, are virtually lossless.

Good weekend,

Al W6LX

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Wes Stewart-2

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

I haven't been following this too closely but...

In a Zo matched system, e.g. network analyzer, reflected power is burned up in
the instrument. So "mismatch loss" is real loss and shows up in s21. Think of
measuring a crystal filter. The crystals can be very low loss but the insertion
loss is high out of the passband because the filter is a huge mismatch.

I agree however with the conclusion.

On 2/16/2018 12:46 PM, alorona wrote:

> Hi,
>
> Okay, I thought your measurements were like S21 and could be considered a
> transmission (thru) loss. The other measurements I referred to were -- in
> other words, I don't believe they were measurements of 'mismatch loss'. The
> Times Microwave loss figure was definitely a transmission loss.
>
> I think it's clear that UHF connectors, at HF, are virtually lossless.
>
> Good weekend,
>
> Al W6LX
>