Open Roads Radio forum for Ham, Amateur Radio and RV camping


Reply
 
Thread Tools Display Modes
 
Old 05-05-2013, 11:13 AM   #1
SoCalRVer
Junior Member
 
Join Date: Mar 2013
Posts: 18
Default New GP antenna, insulate from Mast?

I recently moved my radio shack from my motorhome into my house. I mounted a 4 foot piece of EMT pipe to a vent pipe on my roof and attached the antenna. The antenna is an Arrow GP 144/440. It looks like a J-pole with radials pointed down about 45 degrees. I used tie wraps to secure the RG-8X coax to the mast. My radio is a Yaesu FT-1900 mobile.
I am getting out fine to the local repeater which has perfect line of sight. Using the radio for simplex is interesting. I seem to be getting out fine except that when I check in on a Net, I am able to get a good signal from all except the Net Controller. He is about 5 miles southwest. Another station responding is another 2 miles away and also southwest. I can read him full quieting, great signal.
My question is, mounting the antenna to a metal mast that is probably grounded thru my sewer line causing me lose of signal? If so, how can I insulated it? Also, can turning the antenna with the J-pole section a certain direction help?
SoCalRVer is offline   Reply With Quote
Old 05-05-2013, 03:45 PM   #2
W5DOK
Old Member
 
W5DOK's Avatar
 
Join Date: Oct 2010
Location: In Gods country
Posts: 253
Default

I used PVC split in half to insulate mine. I was mounted on an inch and half pipe so I split a 2 inch piece of pvc and it works fine. The J pole may be a little directional, but probably not much. Wouldn't hurt to check it with a FS meter.
Doc
W5DOK is offline   Reply With Quote
Old 05-05-2013, 03:48 PM   #3
Andy N1ORK
Senior Member
 
Andy N1ORK's Avatar
 
Join Date: Jan 2008
Location: Manchester, CT
Posts: 1,034
Send a message via Yahoo to Andy N1ORK Send a message via Skype™ to Andy N1ORK
Default

Usually the mounting of the antenna is at ground level because the ground for the coax is connected there. So, you should be ok on the vent pipe. The radials are also at ground, so there should be no problem there. Depending on what is between you, how much power you run and the net control 5 miles away may be an issue. I assume he is listening to you simplex on the input of the repeater. I don't think you should insulate it and turning the j-pole may not make any difference.
Post a photo so we can see what it looks like.
73 and good luck!



__________________
CQ..CQ..CQ..DE ANDY, N1ORK..QTH Manchester, CT...QRZ..QRZ..
Hello anyone out there?
Is this thing on?
SkyWarn, CERT, EmComm
Andy N1ORK is offline   Reply With Quote
Old 05-05-2013, 07:10 PM   #4
SoCalRVer
Junior Member
 
Join Date: Mar 2013
Posts: 18
Default

Here are some photos of the antenna and pole. I spray painted the pole black.

As you can see it looks like a small J-pole.

Only running 50 watts at most. It's up about 20-25 feet off the ground. Coax runs across roof, under eaves, down exterior wall and under the house 3 feet.
SoCalRVer is offline   Reply With Quote
Old 05-05-2013, 08:37 PM   #5
NN5I
Carl, nn5i
 
NN5I's Avatar
 
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
Default

It's a ground-independent antenna, so insulating it from the mast, or not insulating it from the mast, ought to make exactly no difference at all.
__________________
-- Carl
NN5I is offline   Reply With Quote
Old 05-05-2013, 08:54 PM   #6
SoCalRVer
Junior Member
 
Join Date: Mar 2013
Posts: 18
Default

Can rotating the antenna improve signal?
SoCalRVer is offline   Reply With Quote
Old 05-06-2013, 05:07 AM   #7
Andy N1ORK
Senior Member
 
Andy N1ORK's Avatar
 
Join Date: Jan 2008
Location: Manchester, CT
Posts: 1,034
Send a message via Yahoo to Andy N1ORK Send a message via Skype™ to Andy N1ORK
Default

Quote:
Originally Posted by SoCalRVer View Post
Can rotating the antenna improve signal?
It may, but may not be worth the trouble. I have an Arrow 2/440 j-Pole (without radials) and it makes no difference.
73



__________________
CQ..CQ..CQ..DE ANDY, N1ORK..QTH Manchester, CT...QRZ..QRZ..
Hello anyone out there?
Is this thing on?
SkyWarn, CERT, EmComm
Andy N1ORK is offline   Reply With Quote
Old 05-06-2013, 07:49 AM   #8
SoCalRVer
Junior Member
 
Join Date: Mar 2013
Posts: 18
Default

Thanks Andy. We don't get much lightning here where I live and I'm some what low compared to other structures. Since the antenna is attached to the vent pipe going right thru the middle of my house, I should probably install some sort of lightning protection. Any suggestions? Something not too expensive please. I can't just throw the coax out the window and it goes under the house for 3 feet and comes up in a bedroom/office.
SoCalRVer is offline   Reply With Quote
Old 05-06-2013, 07:54 AM   #9
N3LYT
Senior Member
 
Join Date: Jun 2012
Location: Maine
Posts: 709
Default

I live in the mountains of western Maine and I can tell you terrain has a LOT to do with reception. One of our repeaters is about 6 air miles from my house and I can barely get into it with a hand held yet another one is in NH 15 miles away and I have no problem with that one. I am often accused of being off freq into a distant UHF repeater because of the multipath from the mountains.
N3LYT is offline   Reply With Quote
Old 12-13-2015, 10:22 AM   #10
KL7V
Junior Member
 
KL7V's Avatar
 
Join Date: Dec 2015
Location: Fairbanks, Alaska
Posts: 12
Default

Probably a terrain issue. Rotating the antenna will probably make no difference it is an omni. Your best bet is more height.
KL7V is offline   Reply With Quote
Old 12-15-2015, 10:47 AM   #11
wa8yxm
Senior Member
 
Join Date: Nov 2007
Location: Mobile, on the road
Posts: 1,139
Send a message via AIM to wa8yxm Send a message via Yahoo to wa8yxm Send a message via Skype™ to wa8yxm
Default

A J Pole it is not (though I do admit it looks like one) J Poles do not need radials or Ground planes. Grounding the mount should, in theory, make no difference on that style of antenna.
wa8yxm is offline   Reply With Quote
Old 12-15-2015, 05:47 PM   #12
NN5I
Carl, nn5i
 
NN5I's Avatar
 
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
Default

Quote:
Originally Posted by SoCalRVer View Post
Can rotating the antenna improve signal?
Only if it's not pointing straight up (or straight down). If it is neither straight up nor straight down, then rotating it so it points straight up or down will improve the signal into other stations' vertically polarized antennas.

Not having it straight up or down will reduce the received signal strength (for each of you) by the square of the cosine of the angle by which it deviates from being parallel to the other guy's antenna. If the "other guy" is a repeater, his antenna almost always points straight up.

Ummm -- perhaps you meant rotating it about a vertical axis. No, that won't do squat.
__________________
-- Carl
NN5I is offline   Reply With Quote
Old 12-15-2015, 08:44 PM   #13
NN5I
Carl, nn5i
 
NN5I's Avatar
 
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
Default

Quote:
Originally Posted by wa8yxm View Post
A J Pole it is not (though I do admit it looks like one) J Poles do not need radials or Ground planes. Grounding the mount should, in theory, make no difference on that style of antenna.
It certainly looks like a J-pole. Why do you say it isn't one?

The presence of 1/4-wave radials doesn't mean it isn't a J-pole. J-poles are almost never a perfect match to the feedline, and it is often useful to provide some sort of choke to prevent RF from flowing on the outside of the coax. Such a choke can be a coiled bit of the coax, or a ferrite toroid (which is what I use on my J-poles) or -- ta-da! -- quarter-wave radials.

It may not be a J-pole anyway, of course; just wondered why you seem so sure it isn't.

A closer photo would enable us to see how it's fed. Then we could tell for sure.
__________________
-- Carl
NN5I is offline   Reply With Quote
Old 12-16-2015, 09:09 AM   #14
N3LYT
Senior Member
 
Join Date: Jun 2012
Location: Maine
Posts: 709
Default

Maybe the problem is the net controller guy! If you are using UHF it can be flaky I have a high gain VHF/UHF repeater antenna on my tower from one direction it is shaded about 50% by the house our VHF repeater and our UHF one are at the exact same location. On VHF I can hear HT's in Conway NH about 15 miles west. The UHF repeater I get about 1/2 scale the VHF full scale. If I walk outside on the other side of the house with an HT I can talk to the the UHF repeater with 5 watts and receive it full scale.
N3LYT is offline   Reply With Quote
Old 12-16-2015, 10:18 PM   #15
NN5I
Carl, nn5i
 
NN5I's Avatar
 
Join Date: Sep 2011
Location: Tallahassee, FL
Posts: 1,441
Default

Quote:
Originally Posted by W5DOK View Post
... I was mounted on an inch and half pipe ...
Trying to visualize Doc mounted on a pipe. Doc, were you punished by impalement?

From The Devil's Dictionary, Ambrose Bierce, about year 1890:

Impale, v.t.
In popular usage to pierce with any weapon which remains fixed in the wound. This, however, is inaccurate; to impale is, properly, to put to death by thrusting an upright sharp stake into the body, the victim being left in a sitting position. This was a common mode of punishment among many of the nations of antiquity, and is still in high favor in China and other parts of Asia. Down to the beginning of the fifteenth century it was widely employed in "churching" heretics and schismatics. Wolecraft calls it the "stoole of repentynge," and among the common people it was jocularly known as "riding the one-legged horse." Ludwig Salzmann informs us that in Thibet impalement is considered the most appropriate punishment for crimes against religion; and although in China it is sometimes awarded for secular offences, it is most frequently adjudged in cases of sacrilege. To the person in actual experience of impalement it must be a matter of minor importance by what kind of civil or religious dissent he was made acquainted with its discomforts; but doubtless he would feel a certain satisfaction if able to contemplate himself in the character of a weather-cock on the spire of the True Church.


The historical Romanian statesman Vlad the Impaler was Bram Stoker's inspiration for his famous novel Dracula. In Romanian, the moniker Vlad the Impaler is Vlad Dracul.

But perhaps, instead, Doc meant something like this verse of The Erie Canal, a song I learned long ago, about age five, from a Burl Ives recording:

The cook she was a grand old gal,
She wore a ragged dress.
We h'isted her up on a pole
As a signal of distress.
Oh, the E-Ri-E was a-risin'.
And the gin was a-gettin' low,
And I scarcely think we'll get a drink
Till we get to Buffalo-o-o,
Till we get to Buffalo.
__________________
-- Carl
NN5I is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 07:00 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
×