RFI mitigation tips for mobile Ops
 

Hey all,

I installed a Bugcatcher in my vehicle last year, and thought I might
share some tips from my experience.

1. Power supply.

Run separate wires for power. Don't try to run an HF rig off a cigar
lighter outlet. I don't care if is an FT-817.....

2. Ground, ground, ground

Getting the "other half" of the antenna to work well is probably the
most important thing you can do. As well as providing the "ground", it
eliminates a lot of little antennas that can give you RFI headaches.

I used coax shield with lugs soldered onto the ends to bond everything.
Keep them as short as practical. Mine were around 4 inches, the longest
around 6 inches. In most cases, the bond can be made by using bolts that
are already on the vehicle. In a few cases I had to drill and bolt. Be
careful of where vehicle wires are already running.

Bond the hood on both sides, all the doors, the hatch if there is one.
Don't forget to bond the exhaust pipe in at least 2 places. The exhaust
even looks a little like an antenna.

Bond the radiator, especially if it is one of the newer ones that have
plastic ends. There is usually some place on the metal part that has a
bolt you can attach to.

Bonding the engine is mandatory. If your vehicle has a frame, like mine
does, bond the frame to the body at several locations.

I probably ended up with 30 different places when I bonded.

3. Ferrites are your friends

I used clip on ferrites. These worked well, and were something around a
dollar a piece.

Clip them on:

Alternator wires, battery wires, radiator fan wires, gas pump power
wires, radio speaker wires, ignition coil wires (some engines now have a
separate coil for each cylinder. If you can reach your wiper motor and
washer pump motor clip one on there also.

If you can get a ferrite on the dreaded main computer module it would be
a big help also. I just happened to have a big clip on from an old IBM
computer that fit around the cable of my computer unit.


4. Look for other sources.

After all the corrections I made, I suddenly found S9 level noise on
HF. I looked to see if ferrites had fallen off, or a bond failed. I
bought a cheap transistor radio to sniff out the problem.

Turns out that my inverter for my laptop is really noisy. I unplugged
it, and the problem went away.

In the end, my mobile HF system is less than S2 (that was as low as I
could test it, seemed to be just around ambient. The only noise source
that I haven't beat yet is the cruise control, and I can just avoid
using that. Finally, I have to remember to keep the car stereo turned
off while transmitting, otherwise I get some strange stuff coming out of
the back speakers.

Oh, and by the way, the antenna appears to work "very well", at least
I've gotten good signal reports on 40 and 20, and reasonably good ones
on 75 meters also. It seems to make use of the limited efficiencies we
see with short HF aerials.

Don't know if anyone else has anything to add, but I thought I'd share this.

-73 de Mike N3LI -

RFI mitigation tips for mobile Ops
 

Michael Coslo wrote:
Turns out that my inverter for my laptop is really noisy. I unplugged
it, and the problem went away.

I had the same problem with my cellphone charger.
--
73, Cecil http://www.w5dxp.com

RFI mitigation tips for mobile Ops
 

Cecil Moore wrote in news:KXMNj.2729$%V7.381
@newssvr14.news.prodigy.net:

Michael Coslo wrote:
Turns out that my inverter for my laptop is really noisy. I unplugged
it, and the problem went away.

I had the same problem with my cellphone charger.

If it is the car charger, are there zeners in it?

- 73 de Mike N3LI -

RFI mitigation tips for mobile Ops
 

Strangely enough, I took absolutely NONE of these precautions - and my
mobile is working nicely. (that doesn't mean I recommend ignoring Mike's
points!)

I'm even running it from the lighter outlet. Figured it would be OK
for the ride home from Milwaukee running 20 watts or so. Kept creeping u
p
the power, I'm now at 80 watts (all bands) & not a hint of trouble.

Again, I don't recommend it though!

The biggest source of QRN are leaky powerline insulators. Next biggest
source are passing semis. (last time I was HF mobile, semis were quiet.
Obviously something has changed in the typical truck engine?)

On Thu, 17 Apr 2008 13:56:06 -0400, Michael Coslo wrote:
Oh, and by the way, the antenna appears to work "very well", at least
I've gotten good signal reports on 40 and 20, and reasonably good ones
on 75 meters also. It seems to make use of the limited efficiencies we
see with short HF aerials.

My Hamsticks are quite effective on 40 - can work pretty much anyone I ca
n
hear if there isn't a pileup, and sometimes even when there is. Managed
to work a VK6 on 40 at sunset on my way into town a few months back -
that's darned near the antipodes from here. Managed to work VP6DX on 80
from the car! Strangely 20 doesn't work quite so well, though I still
work plenty of DX.

RFI mitigation tips for mobile Ops
 

Mike Coslo wrote:
Cecil Moore wrote:
Michael Coslo wrote:
Turns out that my inverter for my laptop is really noisy. I unplugged
it, and the problem went away.
I had the same problem with my cellphone charger.

If it is the car charger, are there zeners in it?

Sorry, I don't know. It must be a switching
supply instead of just a heat-generating
series regulator.
--
73, Cecil http://www.w5dxp.com

RFI mitigation tips for mobile Ops
 

Doug Smith W9WI wrote in
:

Strangely enough, I took absolutely NONE of these precautions - and my
mobile is working nicely. (that doesn't mean I recommend ignoring
Mike's points!)

I'm even running it from the lighter outlet. Figured it would be OK
for the ride home from Milwaukee running 20 watts or so. Kept
creeping up the power, I'm now at 80 watts (all bands) & not a hint of
trouble.

Again, I don't recommend it though!

The biggest source of QRN are leaky powerline insulators. Next
biggest source are passing semis. (last time I was HF mobile, semis
were quiet. Obviously something has changed in the typical truck
engine?)

On Thu, 17 Apr 2008 13:56:06 -0400, Michael Coslo wrote:
Oh, and by the way, the antenna appears to work "very well", at least
I've gotten good signal reports on 40 and 20, and reasonably good
ones on 75 meters also. It seems to make use of the limited
efficiencies we see with short HF aerials.

My Hamsticks are quite effective on 40 - can work pretty much anyone I
can hear if there isn't a pileup, and sometimes even when there is.
Managed to work a VK6 on 40 at sunset on my way into town a few months
back - that's darned near the antipodes from here. Managed to work
VP6DX on 80 from the car! Strangely 20 doesn't work quite so well,
though I still work plenty of DX.


Interesting! Your car being much more quiet might be the result of a
couple things. It is quite possible that you done good in the purchase.
Another possibility is that the bugcatchers are kind of a tour de force
in mobile antennas, and are designed to push every parameter in order to
maximaze efficiency as much as possible in the HF-unfriendly dimensions
available. High-Q coils (which even screwdrivers lack) and the necessary
short lengths of the entire antenna make all mobile HF setups pretty
marginal.I'm one inch short of the maximum height allowed for a vehicle
on US roads. The penalty for this is that the bugcatcher tunes extremely
sharply. I have 2 taps on the coil for 75 meters, and I'd probably need
several more to extend to 80 meters. On 40 and up, one tap per band is
usually sufficient.

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

Has some results of a shootout of various mobile antennas.

Now all that being said, there is a lot of work in putting my HF mobile
setup together. I wanted/needed to tweak out every bit of performance
available for mobile contesting, and was willing to put the time into
it, which ended up being quite a lot of time. I did get to try it out
in the CAQSO party, and it worked okay on 20 meters, PA to CA. I got
good signal reports up and down the east coast on 40. On 80, well, they
didn't ever ask me to repeat myself. But anything below 40 meters is
dicey in operating mobile. I didn't get to use it in the PAQSO which was
my main reason for putting it together, due to a death in the family.
Later this year, I'll do a more scientific test, as much as one can be
done with antennas by someone without access to an antenna range....

And oh yeah - the bugcatcher is quite a sight, especially on a little
Suziki Vitara, even more so, with a 20 inch capacity hat on it. Not
everyone wants to look like that.

- 73 de Mike N3LI -

RFI mitigation tips for mobile Ops
 

On Sun, 20 Apr 2008 22:53:55 -0400, Mike Coslo wrote:
Interesting! Your car being much more quiet might be the result of a
couple things. It is quite possible that you done good in the purchase.

2002 Ford Focus ZX3. Not selected for RF quietness. (when I bought it I
had no plans to operate mobile below 144MHz) Obviously it *is* reasonabl
y
quiet in terms of radiated RF, though conducted RF into the AM BCB radio
is pretty bad! (often the IC-706, with a 40m Hamstick, receives AM BCB
stations better than the car's own radio.....)

Unfortunately it's got 150,000 miles now & I'm starting to think about th
e
next vehicle. Guess I should take along the TH-F6 and a dozen feet of
wire or something.

Another possibility is that the bugcatchers are kind of a tour de force
in mobile antennas, and are designed to push every parameter in order t
o
maximaze efficiency as much as possible in the HF-unfriendly dimensions
available. High-Q coils (which even screwdrivers lack) and the necessar
y
short lengths of the entire antenna make all mobile HF setups pretty
marginal.I'm one inch short of the maximum height allowed for a vehicle
on US roads. The penalty for this is that the bugcatcher tunes extremel
y
sharply. I have 2 taps on the coil for 75 meters, and I'd probably need
several more to extend to 80 meters. On 40 and up, one tap per band is
usually sufficient.

At least on 40 that's wider than my Hamstick. Two settings are necessary
for useful operation across the band (one for CW and one for phone) and
even that's marginal. Never tried 80 without the tuner. 20/15/10 are
indeed useful without retuning.

My solution was to buy a LDG AT-7000 autotuner. I didn't expect much.
(just to be able to get full power from 7000 to 7050 without stopping to
retune) I have been VERY happily surprised. Not only does the tuner
promptly present a decent match to the radio across the entire 40m band
without adjusting the antenna, but efficiency is quite reasonable. No
problems in working DX from 7000 to 7300. With the 20m Hamstick in place
the autotuner also allows work on 30 and 17m - not very well, but it *is*
possible to make QSOs.

The efficiency may not be the best. But it does work, and pretty well.

Now all that being said, there is a lot of work in putting my HF mobile
setup together. I wanted/needed to tweak out every bit of performance
available for mobile contesting, and was willing to put the time into
it, which ended up being quite a lot of time. I did get to try it out
in the CAQSO party, and it worked okay on 20 meters, PA to CA. I got
good signal reports up and down the east coast on 40. On 80, well, they
didn't ever ask me to repeat myself. But anything below 40 meters is
dicey in operating mobile. I didn't get to use it in the PAQSO which wa
s
my main reason for putting it together, due to a death in the family.
Later this year, I'll do a more scientific test, as much as one can be
done with antennas by someone without access to an antenna range....

Mine kinda grew out of a FT-8900R installation. Was enjoying the heck ou
t
of 10m FM (and 6) but they weren't open enough. So I bought the 706 &
started gradually adding bands.

It probably would have made more sense to buy a Bugcatcher. (probably
cheaper than five Hamsticks and an autotuner)

Have used it in the TN QSO Party to the tune of 300-something QSOs. Also
the KY contest two years ago.

And oh yeah - the bugcatcher is quite a sight, especially on a little
Suziki Vitara, even more so, with a 20 inch capacity hat on it. Not
everyone wants to look like that.

One day with a previous mobile, I was listening to 27.185 for some reason
& heard a couple of truckers commenting about the "weird porcupine car"
with all the antennas. This thing probably triggers similar comments.
BCB rubber duckie, VHF/UHF tribander (antenna handles 222 but the radio
doesn't...), HF antenna, and then a second 2m antenna for occasional APRS
..
Then if the bike rack is on the car.....