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Author Topic: HT with a roof antenna  (Read 6672 times)
KE7KTR
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Posts: 15




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« on: January 04, 2012, 02:27:50 PM »

Just trying to learn on the subject...

Has anyone used an HT from indoors with some coax connected to a roof mounted antenna?

Yes, I know that this wouldn't be an ideal setup due to wattage and other limitations and a purpose built base station or even a mobile rig would be preferred. 

Even so, is it doable?  Would the higher elevation / outdoor / higher performance antenna add a significant amount of performance for an HT?

Just wondering.
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KE4YOG
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Posts: 182




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« Reply #1 on: January 04, 2012, 02:49:47 PM »

I would say it would help as long as you use an appropriate antenna. The higher the better to a certain extent as long as the loss from the coax doesnt hurt. I would think that you would be happy with the results as long as you understand the limitations. If you are using a dual band loss on 440 can really be a handicap.
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K1CJS
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« Reply #2 on: January 04, 2012, 03:46:38 PM »

Usually a setup like that will have no problem working.  Just make sure that you have a good coax with a good connectors on both ends. 
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VE3FMC
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« Reply #3 on: January 04, 2012, 03:49:50 PM »

Sure that setup will out perform the rubber duck antenna on the HT. Hands down.
However you must remember this.

An HT has low output. So in order for the majority of that 5 watts to reach the outdoor antenna you are going to need low loss coax as feed line.

LMR 400 would be the minimum I would be running especially if you are going to use the HT on 440. The shorter the run of coax the better. Plus buy the best antenna you can afford to mount on the roof and get it is high as possible.

LMR 400 is stiff coax so you can not bend it much. You need to have big wide bends in that coax if you need to bend it at all. Connecting it directly to the HT would be best, as long as you have a hand held mic you can use. The use of a patch cable between the LMR 400 and the HT will only degrade the performance.

If you do not need a HT, in other words if all you are going to use it for is in the house I would sell it and buy a mobile rig. More power available.
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KA0UAX
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« Reply #4 on: January 04, 2012, 04:13:37 PM »

It should work great if you use low loss cable. I have done this for years with a  2meter radio and a scanner. I use a ground plane under the mobile antennas (sheet metal) in my attic .

ka0uax
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KE7KTR
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« Reply #5 on: January 04, 2012, 05:31:45 PM »

Thanks for the replies.  I don't have any plans right now.  Like I said, just trying to learn about the subject from the experts.  I've heard people say that it's a bad idea, but aside from the obvious limitations, no one has said why it wouldn't work.
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K3WEC
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« Reply #6 on: January 04, 2012, 05:40:22 PM »

It WILL work better using the caveats that the others have stated above.   You're getting your antenna higher and further away from the house wiring.   A quick experiment would be to climb on your roof and see how many more repeaters you can hit vs. sitting in your house.   The efficiency of a decent outdoor antenna should more than make up for the cable loss when weighed against using the rubber duck you likely have now.
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W8JX
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« Reply #7 on: January 04, 2012, 05:41:40 PM »

d
Sure that setup will out perform the rubber duck antenna on the HT. Hands down.
However you must remember this.

An HT has low output. So in order for the majority of that 5 watts to reach the outdoor antenna you are going to need low loss coax as feed line.

LMR 400 woul be the minimum I would be running especially if you are going to use the HT on 440. The shorter the run of coax the better. Plus buy the best antenna you can afford to mount on the roof and get it is high as possible.



No need for LMR 400 here at all. WAY overkill. You will see such a improvement over attached negative gain HT antenna in house that even with 3 or 4 db or line loss the difference will be huge over not doing it. If run is less than 50 ft or so you could even uses RG8x for whole run for 2m. If 440 you should use at least 213 for 50 or so run minimum. Do use RG8x as a pigtail on HT though.
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WB6BYU
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Posts: 13139




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« Reply #8 on: January 04, 2012, 10:05:55 PM »

Yes, this can work, but it may have some unwelcome surprises.

HTs are designed to be used with inefficient antennas.  As a result, the receivers
are very sensitive, but don't handle strong signals very well.  When you put a good
outdoor antenna on one, suddenly signals are much stronger - depending on your
RF environment you may hear spurious signals from paging transmitters (which are
particularly strong), intermodulation, and various other side effects from the
receiver in your HT being overloaded.

Now, even in such cases, the radio will still work, you may just hear a lot of garbage
that you'd rather not listen to.  You won't know that until you try it.


 But if all you have is an HT, go ahead and put an external antenna on it and see how
well it does.  Getting the antenna above the peak of the roof will make a big difference,
though even putting it in the attic may be worthwhile (depending on the roof and
building materials involved.)  A simple ground plane is easy to make.

Some folks get carried away about the need for low-loss coax. You know, if all you
have handy is a 25' length of RG-58 coax, go ahead and use it.  The gain from the
added antenna height will be far more than the loss in the cable.  If that is sufficient
to hit all the local repeaters of interest (especially at low power) then you don't need
to improve it any further.  (You can even use RG-6 CATV coax if that is what is in
your junkbox.)  If you are going to buy coax, consider something better like RG-8X,
RG-213 or some of the low loss foam cables (especially for longer lengths.)  It is only
worth buying more expensive cable when it will make a difference in your ability to
work the stations you want to work:  if you can work all the repeaters you can hear
using low power, there isn't any reason to upgrade your coax, as it won't make any
difference.  (That's because, if you can't hear the repeater now, changing the coax
won't make enough dB of difference to let you work the repeater on your HT.)
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KC2ZPK
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« Reply #9 on: January 05, 2012, 08:27:17 AM »

how about  a RX pre amp and TX amp???
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John
KC2ZPK.com - A work in progress
K3WEC
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Posts: 260




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« Reply #10 on: January 05, 2012, 01:11:58 PM »

By the time you buy those you might as well get a used (or new) mobile.
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W8JX
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Posts: 5629




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« Reply #11 on: January 05, 2012, 01:53:03 PM »

By the time you buy those you might as well get a used (or new) mobile.

I agree before i would buy a amp/preamp combo for a HT it would just but a new or used mobile VHF rig.
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WB6BYU
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Posts: 13139




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« Reply #12 on: January 05, 2012, 06:23:42 PM »

RX preamp probably won't help much - the receiver in an HT is usually pretty sensitive
to start with.  A filter to keep the crud out would be more useful.

You can get used 2m rigs in the $50 to $100 range, which will be much more
suitable than trying to use an amp on an HT.  And consider it even if 5 watts is
enough - if you use the radio a lot, a mobile rig on low power is still a better
solution than an HT.  The HT will get pretty hot if you use it long at full power.


But the antenna will make the most difference.  Put that up first and see how it works.
You may find that it does everything you need.  I put an IsoPole up at 25 feet and
could hit every 2m repeater within 40 or 50 miles using an HT.  (At my present location
I could hit repeaters on 34 out of the 40 2m channels running 2 watts.  There may be
more than that now, but I'd have to figure out all the tones.)  But you won't know
until you try it.
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ONAIR
Member

Posts: 1738




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« Reply #13 on: January 05, 2012, 07:22:04 PM »

Just trying to learn on the subject...

Has anyone used an HT from indoors with some coax connected to a roof mounted antenna?

Yes, I know that this wouldn't be an ideal setup due to wattage and other limitations and a purpose built base station or even a mobile rig would be preferred. 

Even so, is it doable?  Would the higher elevation / outdoor / higher performance antenna add a significant amount of performance for an HT?

Just wondering.
  When I first got my ticket, I had an HTX-202 with the standard duck antenna.  I decided to build a 2 Meter ground plane and stick it on the chimney!  The difference was amazing.  With 5 Watts, I was able to hit many of the repeaters in my area (there were plenty since I was in NYC!)  It's definitely something I would recommend trying.
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W7ETA
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Posts: 2528




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« Reply #14 on: January 06, 2012, 02:09:15 AM »

You can build a vertical dipole using just a chassis mount SO239 and hang it from your celling.

GPs are easy to make with a chassis mount SO239.

I had an old disk-cone scanner antenna that I never used.  I put that on a chimney and ran some coax I had laying around to my HT--it worked FB.

73
Bob
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