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K3 Intermittently loses gain

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Ron W3ZV

K3 Intermittently loses gain

Started to play in the CQWWSSB. K3 started to exhibit intermittent loss
of gain after a transmission. Sometimes, stomping on the foot switch
brings it back up. Sometimes it takes a short transmission. No real
pattern to when it occurs. Receiver isn't totally deaf. Just way down.
Any ideas as to where the problem might be? I'm guessing its time for
the radio to take a trip home to the left coast.

Ron W3ZV
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k6dgw

Re: K3 Intermittently loses gain

Maybe not Ron. This was happening to me, on my K2, K3, and TS-850 when
I still had it. The problem turned out to be a bad connection where the
feedline was connected to the radiator. It didn't happen all the time,
but when it did, a short burst of RF seemed to complete the connection.
Easy fix, hasn't happened since.

I imagine it could have been anywhere between the coax connector on the
radio and the radiator, and connectors would be the first place I'd look
before climbing the tower. OK ... I don't climb my tower anymore.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org

On 10/30/2010 12:20 PM, Ron W3ZV wrote:
> Started to play in the CQWWSSB. K3 started to exhibit intermittent loss
> of gain after a transmission. Sometimes, stomping on the foot switch
> brings it back up. Sometimes it takes a short transmission. No real
> pattern to when it occurs. Receiver isn't totally deaf. Just way down.
> Any ideas as to where the problem might be? I'm guessing its time for
> the radio to take a trip home to the left coast.
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Guy, K2AV

Re: K3 Intermittently loses gain

I agree, this sounds like something loose where transmitting can burn
it. Most of the time this has been something out in the weather.
Sometimes something so simple as a PL259 that didn't get tightened up.
Has also been ruined relay contacts in the amp subjected to hot
switching. Causes for that are diverse. Very easy to do if you are
using a hot mic and VOX.

Good luck & 73, Guy.

On Sat, Oct 30, 2010 at 3:44 PM, Fred Jensen <[hidden email]> wrote:

> Maybe not Ron. This was happening to me, on my K2, K3, and TS-850 when
> I still had it. The problem turned out to be a bad connection where the
> feedline was connected to the radiator. It didn't happen all the time,
> but when it did, a short burst of RF seemed to complete the connection.
> Easy fix, hasn't happened since.
>
> I imagine it could have been anywhere between the coax connector on the
> radio and the radiator, and connectors would be the first place I'd look
> before climbing the tower. OK ... I don't climb my tower anymore.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2011 Cal QSO Party 1-2 Oct 2011
> - www.cqp.org
>
> On 10/30/2010 12:20 PM, Ron W3ZV wrote:
>> Started to play in the CQWWSSB. K3 started to exhibit intermittent loss
>> of gain after a transmission. Sometimes, stomping on the foot switch
>> brings it back up. Sometimes it takes a short transmission. No real
>> pattern to when it occurs. Receiver isn't totally deaf. Just way down.
>> Any ideas as to where the problem might be? I'm guessing its time for
>> the radio to take a trip home to the left coast.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Ron W3ZV

Re: K3 Intermittently loses gain

In reply to this post by Ron W3ZV

Thanks everyone. To respond to the numerous good suggestions, happens on
all bands, but I use one antenna for all bands. I started the contest
with my antenna coming direct to the K3. Not having much luck, I changed
to the amp/external tuner. Happened both ways. That leaves a couple of
coax connectors, a balun and the ladder line feed. Sounds like the next
step is a quick and dirty antenna to the RX antenna input.

Thanks again.

Ron W3ZV

On 10/30/2010 3:20 PM, Ron W3ZV wrote:

> Started to play in the CQWWSSB. K3 started to exhibit intermittent loss
> of gain after a transmission. Sometimes, stomping on the foot switch
> brings it back up. Sometimes it takes a short transmission. No real
> pattern to when it occurs. Receiver isn't totally deaf. Just way down.
> Any ideas as to where the problem might be? I'm guessing its time for
> the radio to take a trip home to the left coast.
>
> Ron W3ZV
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Jim Brown-10

Re: K3 Intermittently loses gain

On 10/30/2010 2:13 PM, Ron W3ZV wrote:
> That leaves a couple of
> coax connectors, a balun and the ladder line feed. Sounds like the next
> step is a quick and dirty antenna to the RX antenna input.

Step #1 -- VERY IMPORTANT. Look at every coax adapter anywhere in your
station. If it does not say Amphenol on it, or if it does not have a UG
number on it, THROW IT AWAY. I'm talking barrels, Tees, Elbows, UHF to
BNC, UHF to N, etc. The unbranded connectors you buy at hamfests and
from ham dealers are almost always made very cheaply, often fall apart,
often go intermittent, and often overheat and fail.

When I got back on the air in 2003 after a long period of inactivity, I
restocked with these junk connectors, not knowing any better. Over the
next several years, I experienced at nearly a dozen intermittents and
failures that I eventually tracked down to one of them. REAL Amphenol
connectors and adapters are one of the things I always look for at
hamfests flea markets, but I couldn't find enough of them for my
station, so a few years ago, I bit the bullet and bought a bunch of the
real thing new from Allied.

Some examples of the failures. 1) intermittent connections at the coax
barrel spacing two lengths of coax feeding an antenna; 2) a Tee
connector that came with a stacking harness for 6M antennas fell apart;
3) an elbow connecting coax to my antenna tuner overheated after about
one hour of contest operation -- SWR went very high and the connector
was VERY hot when I touched it because the wire inside was a tiny
spring; 4) I've had at least four BNC to UHF or UHF to N connectors fall
apart.

In the world of pro audio where I made my living, we see MANY problems
with junk audio connectors. The good stuff costs more to make, so they
costs more to buy. When they fail, they can cost a lot of time and
trouble. Sometimes they only cause an inconvenience, but sometimes they
can cause something to break, or cause you to have to climb a tower to
replace a bad one. Bottom line -- connectors are a terrible place to
play cheap.

73, Jim K9YC
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Mike Harris

Re: K3 Intermittently loses gain

G'day,

Not having any local suppliers here forces mail order shopping for
such items as coax fittings. Whilst there is certainly junk
aplenty, I have not been let down by the items I've bought from "The
RF Connection". I have paid 2-3 times as much for Amphenol barrels
but not found them any better than good quality imports. My guide
is Teflon dielectric, silver plating and mid price. N-type, BNC and
PL259. Crimp, clamp and solder types. No disappointments, no
failures.

I use Ecoflex coax for my main runs and the fittings are special
size and pricy, upwards of $8 for a PL259 or N-type.

Andrew stuff can be pretty eye watering.

Regards,

Mike VP8NO

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: <[hidden email]>
Sent: Monday, November 01, 2010 1:48 AM
Subject: Re: [Elecraft] K3 Intermittently loses gain

> On 10/30/2010 2:13 PM, Ron W3ZV wrote:
>> That leaves a couple of
>> coax connectors, a balun and the ladder line feed. Sounds like
>> the next
>> step is a quick and dirty antenna to the RX antenna input.
>
> Step #1 -- VERY IMPORTANT. Look at every coax adapter anywhere in
> your
> station. If it does not say Amphenol on it, or if it does not have
> a UG
> number on it, THROW IT AWAY. I'm talking barrels, Tees, Elbows,
> UHF to
> BNC, UHF to N, etc. The unbranded connectors you buy at hamfests
> and
> from ham dealers are almost always made very cheaply, often fall
> apart,
> often go intermittent, and often overheat and fail.
>
> When I got back on the air in 2003 after a long period of
> inactivity, I
> restocked with these junk connectors, not knowing any better.
> Over the
> next several years, I experienced at nearly a dozen intermittents
> and
> failures that I eventually tracked down to one of them. REAL
> Amphenol
> connectors and adapters are one of the things I always look for at
> hamfests flea markets, but I couldn't find enough of them for my
> station, so a few years ago, I bit the bullet and bought a bunch
> of the
> real thing new from Allied.
>
> Some examples of the failures. 1) intermittent connections at the
> coax
> barrel spacing two lengths of coax feeding an antenna; 2) a Tee
> connector that came with a stacking harness for 6M antennas fell
> apart;
> 3) an elbow connecting coax to my antenna tuner overheated after
> about
> one hour of contest operation -- SWR went very high and the
> connector
> was VERY hot when I touched it because the wire inside was a tiny
> spring; 4) I've had at least four BNC to UHF or UHF to N
> connectors fall
> apart.
>
> In the world of pro audio where I made my living, we see MANY
> problems
> with junk audio connectors. The good stuff costs more to make, so
> they
> costs more to buy. When they fail, they can cost a lot of time
> and
> trouble. Sometimes they only cause an inconvenience, but
> sometimes they
> can cause something to break, or cause you to have to climb a
> tower to
> replace a bad one. Bottom line -- connectors are a terrible place
> to
> play cheap.
>
> 73, Jim K9YC

Jim Brown-10

Re: K3 Intermittently loses gain

On 11/1/2010 9:37 AM, Mike Harris wrote:
> I have not been let down by the items I've bought from "The
> RF Connection".

I have bought some really lousy junk connectors from the RF Connection,
and when I tried to get real tech info from them on coax they wanted to
sell to a DXpedition, I got nothing but a salesman's bluster.

> I have paid 2-3 times as much for Amphenol barrels

Yes, Amphenol is more expensive than cheap junk. How much does it cost
to get someone to climb a tower? How much do you spend to go on a
DXpedition? How much time do you lose chasing intermittent problems?
> but not found them any better than good quality imports.

How would you KNOW if they are any good or not? Have you cut one open
to see what it looks like? Have you done any serious power tests? Have
you done serious loss or reflection measurements? Have you put stress
on them to break them mechanically?

I used them in my station and nothing blew up (yet)? That isn't a real
test, it's luck.

73, Jim K9YC

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Mike Harris

Re: K3 Intermittently loses gain

G'day,

Under what normal operation usage does a coax connector suffer
sufficient stress to mechanically break it? I've seen connections
fail due to incorrect installation but mechanical breakage due to
poor design, never, at least not on the products I have or would
use. To imply that Amphenol is the only maker of a quality
component is nonsense. I accept that if you buy Amphenol, Suhner,
Greenpar, Aircom, Andrew or similar badged products you know it will
most likely be quality. However, it's not rocket science and there
are undoubtedly many competent manufacturers out there perhaps
without the Mil spec or domestic USA labour rate overheads. There
will always be junk, unfortunately some folks just might not
recognise it as such.

My 6m feeder has US, German and unknown origin fittings in its run,
nothing has failed or deteriorated or shown any signs of overheating
during high power eme operation. My tower is a telescopic/fold over
model so regular maintenance checks are easy and something I'm used
to doing after a career in the rf business, LF to C-band.

Personally, I find the coax terminations within the K3 unappealing
but I'm not going to die in a ditch over it.

Regards,

Mike VP8NO

----- Original Message -----
From: "Jim Brown" <[hidden email]>
Cc: "Reflector Elecraft" <[hidden email]>
Sent: Monday, November 01, 2010 6:59 PM
Subject: Re: [Elecraft] K3 Intermittently loses gain

> On 11/1/2010 9:37 AM, Mike Harris wrote:
>> I have not been let down by the items I've bought from "The
>> RF Connection".
>
> I have bought some really lousy junk connectors from the RF
> Connection,
> and when I tried to get real tech info from them on coax they
> wanted to
> sell to a DXpedition, I got nothing but a salesman's bluster.
>
>> I have paid 2-3 times as much for Amphenol barrels
>
> Yes, Amphenol is more expensive than cheap junk. How much does it
> cost
> to get someone to climb a tower? How much do you spend to go on a
> DXpedition? How much time do you lose chasing intermittent
> problems?
>> but not found them any better than good quality imports.
>
> How would you KNOW if they are any good or not? Have you cut one
> open
> to see what it looks like? Have you done any serious power tests?
> Have
> you done serious loss or reflection measurements? Have you put
> stress
> on them to break them mechanically?
>
> I used them in my station and nothing blew up (yet)? That isn't a
> real
> test, it's luck.
>
> 73, Jim K9YC

KF4VTT

Re: K3 Intermittently loses gain

In reply to this post by Ron W3ZV

Did this problem happen after you connected the amp?

I ran into a similar problem. My external Ameritron T/R relay failed and held the amp in transmit. The only way I realized that the amp was stuck in transmit besides the diminished receive was the heat I noticed coming off the amp. I could see the heat rising against the backdrop of the wall. :-) Thank goodness I did not have drive going to the amp that amount of time. I would be buying a brand new pair of 3-500's. I removed the external T/R relay and started using the internal ability of the K3 to trigger the amp.

Besides checking the ideas from the other guys, check your T/R circuitry for your amp.

73,
Doug
KF4VTT
K3 #1289
P3 #371

Jack Smith-6

Re: K3 Intermittently loses gain

In reply to this post by Mike Harris

The most recent experience I've had is with single hole mount SO-239
connectors, Teflon insulation, purchased the The RF Connection.

I installed six of them in a batch of Norton preamplifiers Friday and
when I plugged a UHF-BNC adapter in to connect some test equipment, I
noticed the center pin rotated inside the Teflon insulator. The center
conductor broke from the windlass effect.

The upshot is that Joel, W3RFC, the owner of The RF Connection
determined that a significant fraction of this part had a manufacturing
defect. These are imports, presumably from China, although I didn't ask.

The defective parts I have will be replaced as soon as the compliant
parts arrive. However, I can't recover the two hours it took to install
the first set of connectors, then remove them, drill the extra holes to
substitute flanged connectors and install flanged connectors. (Which are
also imports, silver/Teflon but higher quality.)

I've lost track of the number of failures with other Chinese adapters.
Some that I remember include a couple of BNC F-F connectors where the
center insulator fell out. Same thing happened with a BNC "T" connector.
I have a BNC-UHF adapter where the UHF shell is unthreaded for half the
length. Two of the same type of adapter had the shell separate from the
body. All the BNC-F adapters I have are extremely tight fitting on the
BNC end.

In the past I've purchased a quantity of Chinese BNC connectors for kits
I sell. While they work, the dimensions are subtlety off someplace so
that they have to be fiddled with to connect to a MILSPEC BNC connector.

So far, the inexpensive Chinese SMA connectors seem fine, however.

I've since switched to Amphenol BNC parts, which are also made in China
but with much better dimensional and quality control.

I suspect my experience is not unique.

Jack K8ZOA

On 11/1/2010 7:06 PM, Mike Harris wrote:

> G'day,
>
> Under what normal operation usage does a coax connector suffer
> sufficient stress to mechanically break it? I've seen connections
> fail due to incorrect installation but mechanical breakage due to
> poor design, never, at least not on the products I have or would
> use. To imply that Amphenol is the only maker of a quality
> component is nonsense. I accept that if you buy Amphenol, Suhner,
> Greenpar, Aircom, Andrew or similar badged products you know it will
> most likely be quality. However, it's not rocket science and there
> are undoubtedly many competent manufacturers out there perhaps
> without the Mil spec or domestic USA labour rate overheads. There
> will always be junk, unfortunately some folks just might not
> recognise it as such.
>
> My 6m feeder has US, German and unknown origin fittings in its run,
> nothing has failed or deteriorated or shown any signs of overheating
> during high power eme operation. My tower is a telescopic/fold over
> model so regular maintenance checks are easy and something I'm used
> to doing after a career in the rf business, LF to C-band.
>
> Personally, I find the coax terminations within the K3 unappealing
> but I'm not going to die in a ditch over it.
>
> Regards,
>
> Mike VP8NO
>
>
>
>
> ----- Original Message -----
> From: "Jim Brown"<[hidden email]>
> Cc: "Reflector Elecraft"<[hidden email]>
> Sent: Monday, November 01, 2010 6:59 PM
> Subject: Re: [Elecraft] K3 Intermittently loses gain
>
>
>> On 11/1/2010 9:37 AM, Mike Harris wrote:
>>> I have not been let down by the items I've bought from "The
>>> RF Connection".
>> I have bought some really lousy junk connectors from the RF
>> Connection,
>> and when I tried to get real tech info from them on coax they
>> wanted to
>> sell to a DXpedition, I got nothing but a salesman's bluster.
>>
>>> I have paid 2-3 times as much for Amphenol barrels
>> Yes, Amphenol is more expensive than cheap junk. How much does it
>> cost
>> to get someone to climb a tower? How much do you spend to go on a
>> DXpedition? How much time do you lose chasing intermittent
>> problems?
>>> but not found them any better than good quality imports.
>> How would you KNOW if they are any good or not? Have you cut one
>> open
>> to see what it looks like? Have you done any serious power tests?
>> Have
>> you done serious loss or reflection measurements? Have you put
>> stress
>> on them to break them mechanically?
>>
>> I used them in my station and nothing blew up (yet)? That isn't a
>> real
>> test, it's luck.
>>
>> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

PTA_ABD

Re: K3 Intermittently loses gain

In reply to this post by Ron W3ZV

I'm reminded of a Field Day a few years ago where tested , tried and true antennas suddenly didn't work anymore ... bad SWR's all over the place, goofy noises, etc. etc.
Re-tested with different analyzers and dummy loads ... they checked out fine... so what's going on when connecting extra coax extensions??? Nobody suspected those brand new "unbadged" double female coax barrels. We didn't bother to dissect them ... just threw them in the lake.

Paul WB2ABD
(w/ K2ZR Buffalo Light House Group FD )
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hb9ari@bluewin.ch

Re: K3 Intermittently loses gain

In reply to this post by Ron W3ZV

Hi Ron,

Hi had a similar problem some months ago.
Symptoms:

Suddenly loss of sensitivity ~ -20 to -40dB or more...
Transmission was always ok.
Measurement with miniVNA always correct (at ~0dBm power).
Moving some connections remove sometimes the loss of sensitivity.
(but all soldered or crimped connections were tested as 100% ok,
no "cold" solder joint, or broken wire, etc)

After searching a lot of time, i suspected "old" silvered connectors,
plugs, etc
Changing all connectors with non silvered ones, all is now perfect!
My explanation, accepted by other OM, is the following:
My "old" idea, (ham since 1970) was that silver oxide was conducting,
may be true, but over an (undefined for the moment...) level.
In RX mode, in the uV range, i suppose that the potential is
insufficient to break the ultra thin sliver oxide layer.
With 0dBm or more "level", the oxide layer should be broken and
all is ok. If i'm correct , some mechanicals relays are not specified
under some voltage levels and to commutate very low voltages,
some "special" kind of metal contacts must be used.
Since this "incident" ALL silvered plated connectors, plug, etc
are banned from the shack ! I never had problem since
i've taken this decision.

My best 73,

Rudi, HB9ARI

Ron W3ZV wrote:

Edward R Cole

Re: K3 Intermittently loses gain

In reply to this post by Ron W3ZV

I wasn't going to reply on the coax connector issue, but how I know
that Amphenol UHF connectors are best is from 15-years of commercial
use in Marine Electronics. They solder better and do not fail like
cheaper manufacturer's. We tried saving some money using RS
connectors in the beginning and had some many problems that I made
the decision to specify Amphenol brand 100% for UHF and N-type.

You do not want coax failures when you need to call the USCG for
assistance because your boat is sinking or on fire.

So I have not done lab measurements, etc. Only tested them in a
demanding environment over a long time period.

For an alternative I use RF Parts connectors for special coax types
or unusual adapters. My 2m eme array uses 20 N-male RF Parts
connectors for Time LMR-400 coax (larger dia. than RG-213). They
have been in service on the tower since 1998. I had one bad SWR but
that was the result of improper assembly. The connector works good
after reassembly.

Answer to tower climbing question: I climb my towers for free. The
Tower service we hired at work charged $120/hour. I am happy that I
can still climb but know the years that I can continue are
limited. Another reason to not take shortcuts on cables and connectors.

73, Ed - KL7UW

------------------------------
Message: 36
Date: Mon, 01 Nov 2010 14:59:22 -0700
From: Jim Brown <[hidden email]>
Subject: Re: [Elecraft] K3 Intermittently loses gain

Yes, Amphenol is more expensive than cheap junk. How much does it cost
to get someone to climb a tower? How much do you spend to go on a
DXpedition? How much time do you lose chasing intermittent problems?

How would you KNOW if they are any good or not? Have you cut one open
to see what it looks like? Have you done any serious power tests? Have
you done serious loss or reflection measurements? Have you put stress
on them to break them mechanically?

I used them in my station and nothing blew up (yet)? That isn't a real
test, it's luck.

73, Jim K9YC

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 144-800*w, 432-100w, 1296-QRT*, 3400-winter?
DUBUS Magazine USA Rep [hidden email]
======================================
*temp not in service
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alsopb

Re: K3 Intermittently loses gain

In reply to this post by KF4VTT

On 11/1/2010 23:36, KF4VTT wrote:

>
> Did this problem happen after you connected the amp?
>
> I ran into a similar problem. My external Ameritron T/R relay failed and
> held the amp in transmit. The only way I realized that the amp was stuck in
> transmit besides the diminished receive was the heat I noticed coming off
> the amp. I could see the heat rising against the backdrop of the wall. :-)
> Thank goodness I did not have drive going to the amp that amount of time. I
> would be buying a brand new pair of 3-500's. I removed the external T/R
> relay and started using the internal ability of the K3 to trigger the amp.
>
> Besides checking the ideas from the other guys, check your T/R circuitry for
> your amp.
>
> 73,
> Doug
> KF4VTT
> K3 #1289
> P3 #371

Any relay in the RF chain can exhibit signal drop out on RX but work
fine on xmit. The problem is usually caused by corroded/burned
contacts. Higher transmit voltage can punch through the corrosion while
weaker signals cannot. This is especially true for relays which are
outdoors. Relay replacement is the only real solution. Contact cleaner
is iffy. Filing the contacts for some relays destroys the plated
contact material and can result in even worse performance.

Some designs use "double contacts" to almost eliminate the problem. Use
paralleled contacts (dpdt relay) or find a relay with "bifurcated"
contacts. These relays have a pole with a "tuning fork" type design.
Each arm has a separate contact. If one contact doesn't work, maybe the
other will.

The same goes for corroded antenna connectors and connections to the
antenna elements.

The real work is in finding which of the above is the culprit.

If one has a low voltage portable RF source, e.g. the XG1, and a buddy
in the shack, one can connect it at various points of the system and
find where the dropout occurs.

73 de Brian/K3KO

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Bill VanAlstyne W5WVO

Re: K3 Intermittently loses gain

In reply to this post by hb9ari@bluewin.ch

This failure modality, I believe, applies equally to all sorts of RF
"connectors", which includes relay contacts as well as cable-end connectors.
I've experienced similar failures twice over the past seven years.

In the most recent case -- and the symptoms were exactly as described in
this thread -- it was the normally-closed (receive) contacts in the frame
T-R relay in the amplifier. I fiddled with that relay for several weeks
trying to get enough contact tension and/or wiping action on the "normally
closed" side, and finally gave up and pitched it in the trash. I designed
and built a completely new T-R system using name-brand high-speed vacuum
relays and have never looked back. It works flawlessly, and at QSK speeds.

One final word -- "Made in China" does not necessarily mean cheap and
shoddy, though it sometimes does. "Made in USA" does not necessarily mean
high-quality, robust construction, though it sometimes does. It just isn't
that simple any more. I have a pair of 3-500ZG triodes, for example, that
came from RF Parts and were undoubtedly made in China. They are workhorse
performers and have withstood years of abuse as well as a high-voltage
glitch that fried a number of other components in the amplifier. On the
other hand, I am with those who use spend the extra money for Amphenol RF
connector parts, not because they are always made in the USA (they aren't,
apparently), but because I trust the COMPANY to produce quality parts in
whatever country they choose to manufacture in.

Bill W5WVO

-----Original Message-----
From: hb9ari
Sent: Tuesday, November 02, 2010 06:25
To: Elecraft-forum
Subject: Re: [Elecraft] K3 Intermittently loses gain

Hi Ron,

Hi had a similar problem some months ago.
Symptoms:

Suddenly loss of sensitivity ~ -20 to -40dB or more...
Transmission was always ok.
Measurement with miniVNA always correct (at ~0dBm power).
Moving some connections remove sometimes the loss of sensitivity.
(but all soldered or crimped connections were tested as 100% ok,
no "cold" solder joint, or broken wire, etc)

After searching a lot of time, i suspected "old" silvered connectors,
plugs, etc
Changing all connectors with non silvered ones, all is now perfect!
My explanation, accepted by other OM, is the following:
My "old" idea, (ham since 1970) was that silver oxide was conducting,
may be true, but over an (undefined for the moment...) level.
In RX mode, in the uV range, i suppose that the potential is
insufficient to break the ultra thin sliver oxide layer.
With 0dBm or more "level", the oxide layer should be broken and
all is ok. If i'm correct , some mechanicals relays are not specified
under some voltage levels and to commutate very low voltages,
some "special" kind of metal contacts must be used.
Since this "incident" ALL silvered plated connectors, plug, etc
are banned from the shack ! I never had problem since
i've taken this decision.

My best 73,

Rudi, HB9ARI

Ron W3ZV wrote:

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Jim Brown-10

Re: K3 Intermittently loses gain

On 11/2/2010 5:12 AM, Bill VanAlstyne W5WVO wrote:
> but because I trust the COMPANY to produce quality parts in
> whatever country they choose to manufacture in.
>

YES! I don't want to get into the politics of this, but the very sad
part is that so many US companies have been forced by world economics to
move their mfg away from the US.

73, Jim K9YC

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Eric Swartz - WA6HHQ

Re: K3 Intermittently loses gain [END of thread]

Administrator

In reply to this post by Bill VanAlstyne W5WVO

Since this thread has drifted off the initial question, and because
we're beating to to death :-) , let's end it for now.

73, Eric
Elecraft list modulator
----

On 11/2/2010 5:12 AM, Bill VanAlstyne W5WVO wrote:
> This failure modality, I believe, applies equally to all sorts of RF
> "connectors", which includes relay contacts as well as cable-end connectors.
> I've experienced similar failures twice over the past seven years.
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