Base Station Antenna

[ljones135]

I'm considering putting up a GMRS base station and I'm looking for some helpful input as to what antenna to use. I'm considering using a magnetic mount mobile antenna on my steel guttering. What coax should I use RG-58 or RG-8? 

[WRAK968]

For less than 50' RG8X is ok (I've used it for ham radio for years without an issue) anything over 50' and I seem to get signal issues.

As for your antenna, you may wish to look for something like this:
https://www.amazon.com/Browning-450MHz-470MHz-Mobile-Fiberglass-Antenna/dp/B00IDTJ3AS/ref=sr_1_5?keywords=GMRS+base+antenna&qid=1561855637&s=gateway&sr=8-5

The antenna is about 2 feet tall and does not require a ground plane to operate. When I had mine I had no SWR issues, (Typically 1.0-1.1:1) I mounted it on the vent pipe for the sewer with a short 1.5" pole and some straps.

There is two reasons why I would stay out of the gutter. A) the magnetic bases arn't small, even a 3" gutter may have a hard time fitting the smaller of reliable antenna bases in it. This leads to clogging of the gutter which can back up into the fascia causing mold and rot issues. Add to it that most mag mounts are merely water resistant and not completely waterproof and you have the makings for a disaster for your radio and house. B ) The gutter isn't wide enough to give you an effective ground plane which is needed for mag mount antennas. Normally, you want your ground plane to be opposite the radiating element (Like a di-pole) or spread evenly around the element. Using the gutter, you would have two directions with good ground plane and the rest where ground plane is non existent. This affects the signal pattern of the radiating element during TX and can throw SWR off. It also can cause issues with RX as the ground plane tends to reflect signals into the element (much like a satellite dish.) Don't get me wrong, it could work and is a better solution to running a 5 watt portable from inside of the house, but if your looking for longer distances your best bet is to go with a true base antenna.

[Logan5]

Get a pole, a house bracket, good quality antenna and feedline. the pole and house bracket cost less than $30 and provides a good place to mount a quality antenna. messing with aluminum gutter work will create all kinds of problems, some already mentioned above. For best results use two poles and a pole to pole bracket and do your best to get the antenna at least 10' above your roofs ridge line. There are lot's of options for mounting a pole to your home, a tilting base is also helpful.

[PastorGary]

Approximate** attenuation per 100 feet of cable at 462 mhz:


Belden 9258 RG8X - 7.15 db

Belden 9913 RG8 - 2.9 db

 

Belden 9201 RG58 - 9.1 db

 

Belden 8267 RG213 - 4.82 db

LMR400 - 2.72 db    (may have long term internal mechanical issues at UHF frequencies)

Heliax 1/2 inch - 1.47 db

[ ** ratings are from manufacturer datasheets for the specific type and series listed. Other manufacturers ratings may be slightly different.]

 

 

 

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[Logan5]

I want to go Heliax 1/2 inch, but I am so afraid of damaging it with a retracting and tilt over Antenna Support Structure. Heliax is not very flexible and I have tight and close quarters around the base. I should just pull the triger and give it a shot.

[wqzw301]

I recently tried lmr240 instead of rg8x.

Works great, better weather protection and shielding.

Also less db loss than 8x on the TIMES MICROWAVE coax comparison chart for uhf...

Just a bit thicker but still pretty flexible. My snap on ferrites fit the same as on rg8x.

Also I went with N connectors instead of UHF.

 

good luck

301

[Logan5]

I ordered 80' of LDF4-50a, and connectors. Plan to do the upgrade in the next week or so..

[WREB270]

I have been considering doing this. I have a 38" antenna with group d plane kit. We have a 2 short home. Wanted to mount it on the roof line/chimney but was worried about lightening strikes (and heights in general). Does anyone tie their roof mounted system into a ground rod? There is a old dish antenna up there, it may have a ground wire already that I can tap into.

 

I read an alternative option is to mount it in the attic. The only obstruction is the roof sheathing. On a two story house this still gets your antenna 25ish feet in the air.

[Logan5]

The attic install is less than ideal. Roof line install is a much better situation. Lightning is much less of an issue if your mast is grounded and you have a grounded inline lighting arrestor. I have a 55' tower 6 years and no strike. Go with the chimney mount and ground, you will be much happier.

[WREB270]

The attic install is less than ideal. Roof line install is a much better situation. Lightning is much less of an issue if your mast is grounded and you have a grounded inline lighting arrestor. I have a 55' tower 6 years and no strike. Go with the chimney mount and ground, you will be much happier.

Ok sounds like a plan. Did you put inline protection at the antenna and at the equipment hook up?

[Logan5]

No, I use a Hoffman environmental enclosure, I drilled a 5/8in hole in the bottom and used a bulkhead style arrestor, with an LMR400 2 foot jumper inside the box. My grounding, grounds the arrestor and the environmental enclosure. I have been told I should ground the tower also, and separately.