Railfan Technology > Antenna recommendations

Hi everyone

My railcom antena has finally bit the dust and was wondering if anyone had any ideas for what is best now, Ive had mione for years.   I have an ICOM V8000 radio.  Any suggestions are appreciated


Gary
 

I have RH77CA by Diamond on all my scanners (4) and on my 2mt/440 ham handheld.
Have not lost one yet. All told about 15 years now.........Swede,,,,,,,,,Albany,OR.........

Gary,

I've got an IC-V-8000 mobile / base unit as well.

I'm surprised your antenna quit. Before springing for a new one,
you may wish to replace the coax starting at the base of the antenna.
Measuring for a short with a DVOM is fruitless as the coil in the
base provides a nearly short DC circuit to ground. If you choose to
try this, PM me and I'll be happy to assist. You will need at least
model railroader level soldering skills.


If you are going to mount the IC-V8000 in your auto / truck, I'd go
with a simple 1/4 wave mag mount.

In increasing order of cost and performance:

1/4 wave mag-mount

1/4 wave permanent mount

5/8 wave mag-mount (likely what your Railcom was)

5/8 wave permanent mount.

For decades, I used a permanent mount 5/8 wave on the van where I had
ample area for an effective ground plane. Got weary of it snagging on
low branches so I switched to a permanent mount 1/4 wave antenna. Have
not noticed any difference in performance.

If you choose to go with another 5/8 wave antenna, be certain it measures
about 42" long. Some folks label their wares with 5/8 in the model number
but absent several concurrent exemptions from the laws of physics....they
simply are not 5/8 wavelength antennas and cannot perform as such.

Also, be wary of claims of 3db more gain compared to a 1/4 wave antenna.
Theory does not support that claim even for ideal conditions. Real world,
about 1.5 dB. I doubt anyone could detect the difference in an A-B test
in the real world with real equipment on a real car / truck wherein one
antenna provided 1.5 dB additional gain.

I'd go with Larsen as a manufacturer,

Be Well,

tim Colbert K3HX

Just order a new mag mount, the railcom base is a rebranded PC-Tel/Maxrad. Replacing coax on a $19 magmount is a tremendous waste of time unless you happen to get into that type of project.

JW

I have a Larsen NMO permanent mount and use the 1/4 wave around town and a 5/8 wave on trips.

I have an MFJ-1412 that I have used for about 10 years or more. It's a dualband antenna for 146 and 440 MHz I chose it because of the one piece construction. It has held up well. The base is plenty strong and I have it on a mag-mount. The only problem I have is when It is on the roof of my truck and I pull into the garage, I often forget to remove it until I hit the door frame. They cost just under $30.00 plus the cost of the mount, magnetic or permanent.

John

I myself have used a 5/8 wave Maxrad antenna on a truck as well with a mag mount on the roof for countless years and had great success with the receive reception. Another location I have seen is a bolted fender mount near the FM radio antenna. Any pointers on how to improve this locations ground plane since its hard mounted (bolted) to the fender. Please feel free to comment, greatly appreciated. Thanks in advance. JR

austin Wrote:
-------------------------------------------------------
> I myself have used a 5/8 wave Maxrad antenna on a
> truck as well with a mag mount on the roof for
> countless years and had great success with the
> receive reception. Another location I have seen is
> a bolted fender mount near the FM radio antenna.
> Any pointers on how to improve this locations
> ground plane since its hard mounted (bolted) to
> the fender. Please feel free to comment, greatly
> appreciated. Thanks in advance. JR

Austin,

The front fender area is a less than optimum place to mount
a VHF RR antenna. I know of no practical way to improve
the ground plane for this situation.

A ground plane should extend like a flat disk with no nearby
obstructions. On an automobile, pickup or van the middle of
the roof most closely approximates this.
Cloth top convertibles excepted. (smile)
Sunroof-equipped cars should have the antenna mounted in the
middle of the metal area of the roof.

The fender mount has an obstruction in the form of the windshield,
frame and passenger compartment. The structure of the windshield,
frame and the passenger compartment may "shadow" the RR antenna.

If the RR antenna is mounted near the factory FM radio antenna
it may be even worse. The FM antenna may act as a reflector and
tend to reject signals coming from behind. In any event, the
FM antenna will distort the RR antenna pattern.

The fender mount also has part of the ground plane "disk" missing
which distorts the pattern even though it may be possible to tune
the antenna for a low VSWR.

Another problem with the front fender bracket mounted antenna is
RF noise from the engine compartment leaking into the lead-in cable
to the radio.

Bracket-mounted antennas on the trunk have the many of the same limitations.

Antennas mounted in the middle of the trunk lid may have an adequate
ground plane but the nearby rear window and passenger compartment
can cause "shadowing."

The hardware in bracket-mounted mobile antennas provides mechanical
attachment and "bonds" the assembly to the chassis but does not
provide sufficient "RF ground" (the ground plane "disk") for optimum
operation.

I'll be glad to answer any questions you have.

Be Well,

Tim Colbert K3HX

PS I'll be at Summerail as a vendor and look forward to meeting TO
folks. Look for my "US Air Force Veteran" hat.