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Author Topic: Workman Hamstick issue.....  (Read 2599 times)
K3NRX
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« on: October 15, 2011, 10:19:36 AM »

My audio cuts out and back in when I move the car....Unless I am stopped, stationary, or going perfectly straight on smooth road, the audio cuts out on my 10 meter Workman during turns and on rougher road.....Bad timing!...Bad Bad Bad, however I managed to work a few EUs the last couple of days from the vehicle....Not sure what the issue is...Could I have a short in the antenna or in the magnet???...Should I take apart the magnet mount???...If it's in the antenna, what do I do???.....Please help

V
KA3NRX

P.S. I use the same mount for my 2 meter whip, and I did not have an issue like this, albeit the 2 meter antenna is much shorter than the Hamstick for 10....

« Last Edit: October 15, 2011, 10:22:37 AM by KA3NRX » Logged
AD6KA
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Posts: 2232




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« Reply #1 on: October 15, 2011, 01:17:39 PM »

Except in emergencies, mag mounts generally make
really lousy mounts, especially on HF, due to lack of good grounding.

I would look into a permanent mount for each band,
and also do some research on better grounding
of the mount to the vehicle, grounding the various
panels of the vehicle to one another, grounding the rig, etc.

(Check all yer cables, toom coax and DC.)

Plus a bunch of other stuff, it's not really my area of expertise but there are tons org great sites all over the INterwebs.,

GL es 73, Ken  AD6KA
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W8JX
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« Reply #2 on: October 15, 2011, 02:29:25 PM »

Except in emergencies, mag mounts generally make
really lousy mounts, especially on HF, due to lack of good grounding.

I have used custom Mag mounts for HF antennas for many years and NEVER had any problems with antenna performance vs a rigid mount or grounding issues.  Never had and problem with VHF/UHF using them over 30 years there. The only "weakness" of a mag mount you need to make sure you use a big enough magnet for the job.
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AC4RD
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« Reply #3 on: October 15, 2011, 04:48:48 PM »

This may not be any help, but I'll offer it anyway.  I used Hamsticks for a while, very happily, on a lip mount on the trunk of a sedan.  It was pretty routine--suddenly I'd have sharp spikes in SWR and drop in signal strength, on and off, or mostly on.  When that happened, I'd take off the lip mount, rub off the corrosion, give things a shot of WD-40, and put the lip mount back on, nice and tight.  That would solve it for the next few weeks. 
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N6AJR
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« Reply #4 on: October 15, 2011, 04:54:45 PM »

I had a  similar problem on my ATAS 120 on the rear deck lid of my car.  it seems that as you drive down the road the lid bounces up and down slightly and it makes intermittant connection for ground through the pins on the hinge.  I ran a piece of braid from the shield ( ground) side of the mount to the body side of the hinge and fixed it.
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WB6BYU
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« Reply #5 on: October 16, 2011, 07:27:19 PM »

Quote from: AC4RD
...It was pretty routine--suddenly I'd have sharp spikes in SWR and drop in signal strength, on and off, or mostly on.  When that happened, I'd take off the lip mount, rub off the corrosion, give things a shot of WD-40, and put the lip mount back on, nice and tight.  That would solve it for the next few weeks. 


The same applies where the antenna screws into the mount - take it out, clean out any corrosion,
put some No-Al-Ox or Ox-Gard on the threads, and reassemble it.

Most likely the problem is an intermittent, either open or short, in the mount somewhere.  It might
be that the antenna just isn't screwed in tight enough.  Could be some corrosion or an intermittent
connection inside the mount, etc.  Could even be on the antenna at the point where the wire
attaches to the bottom ferrule.  You can test it by wiggling the antenna while you are parked to
see if you can reproduce the problem.

If it is the antenna, you can try removing some of the heat shrink tubing at the base and repairing
the connection (which might require a solder lug if you can't make a good connection to the ferrule.)
Otherwise look for corrosion, a broken wire or stray braid inside the mount that is causing an open
or short circuit.  Before disassembling the mount, you might try a different mobile whip (perhaps a
CB whip or whatever else you have handy) to confirm that it is the mount and not the antenna.

It also depends where you have the mount installed - if it is on a small trunk lid, the problem could
be intermittent connection though the hinges as the trunk lid is torqued back and forth by the
whip waving about.  I wouldn't think that this would cause total dropout of the signal, but you do
need a good solid, reliable ground connection from the lid to the frame of the car for reasonable
efficiency.

(If the audio is what is cutting in and out, it could be an intermittent speaker lead as well!)


The problem with mag mounts on HF is that I haven't yet seen one with enough surface area to
provide a low capacitive reactance between the mount and the car though the paint.  On 2m
it takes around 120pf to reduce the reactance to 5 ohms, and with a quarter wave whip your
antenna resistance will be perhaps 35 ohms.  A 10m mobile whip would require 5 times the
surface area to get the same reactance, but the antenna resistance is also going to be lower
if you aren't using a full size quarter wave whip.  While reactance isn't the same as resistance,
it does point out that a mag mount doesn't just perform a mechanical function.

Mobile operation puts a lot of mechanical stress on the mount, especially as antennas get
longer and/or heavier.  Any such mount requires regular inspection, and occasional repair
and/or replacement.  Insulators crack, screws come loose, and corrosion gets in all sorts
of places (especially where you get moisture.)  Looks like a good time to learn how to take
your mount apart and check it out.

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WX7G
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Posts: 5920




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« Reply #6 on: October 17, 2011, 05:35:32 AM »

A test of the antenna and mount integrity:

  • tie a string to the antenna
    as the vehicle is stationary transmit while tugging on the string
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K3NRX
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Posts: 1974


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« Reply #7 on: October 17, 2011, 09:17:46 AM »

Hi guys!...Great advice, as I did just that....Yesterday while watching the Steelers game, I took apart my magnet and cleaned up the points of contact, as, yes, corrosion set in...sprayed some tuner cleaner on it and did some scraping and scratching on the contact point and put it all back together....that seemed to do the trick as the audio no longer cuts out.....worked into Algeria, Russia and Belarus from the car this morning.....I even sprayed the coax connection on the rig just to be sure.....as long as I don't hit any monster potholes or speed bumps at over 20 mph, I think were going to be OK....Thanks!

V
KA3NRX

« Last Edit: October 17, 2011, 09:19:24 AM by KA3NRX » Logged
K2ZS
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Posts: 36


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« Reply #8 on: October 22, 2011, 06:35:09 AM »

It was found by one of our local hams that the "Workman" brand antennas use a copper clad wire for the loading coil and that the clad will delaminate at the top connection. This causes intermittant connections to the stinger and cause these spikes in SWR and loss of audio. Because the coil wire is only clad with copper it is sometimes not possible to re-solder the connection. You may try using a stainless steel hose clamp to secure the wire back to the top fitting but this could increase the wind loading on the antenna.

Hope that helps...
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Antenna restricted?
http://www.k2zs.com
WB6BYU
Member

Posts: 13038




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« Reply #9 on: October 22, 2011, 05:55:23 PM »

If it does come apart, W5DXP shows you how to make a more efficient tunable antenna here:

http://www.w5dxp.com/bugstick.htm

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