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Author Topic: Mounting a Hustler HF antenna on motorhome?  (Read 2179 times)
WB0AXN
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« on: June 02, 2003, 04:45:54 PM »

I've used a Hustler HF mobile antenna (MO-2 mast with RM-20 and 75 coils) for over 30 years on several autos and in my opinion, had very good results making contacts.  

Last week, I mounted the antenna on my motorhome's rear bumper.  The bumper is chromed steel about ten inches wide an eighth inch thick.  The bumper is mounted on two "I" beams which run the length of the motorhome and I figure this will make a decent counterpoise ground?  The body of the motorhome is fiberglass.  My rig tunes up good with a low SWR, but my signals are partially blocked because the antenna coil is below the roof.  I sent an email to Hustler asking if they had a **48 inch extension** for the mast and this is the reply I got from the sales manager:

>>Sorry, no extensions available.  Most customers mount them on a ball mount and that will allow them to get the resonator above the motor home.<<

Evidently, he doesn't realize most motorhomes and campers have non-metalic bodies, such as fiberglass.

My questions are:  Is there a 48 inch extension available from another company?  Is there a better way of mounting an antenna on a motorhome besides the bumper?  How high above the roof is best?   (my home has a metal roof)

Roland



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K0BG
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« Reply #1 on: June 02, 2003, 05:31:19 PM »

If it were mine, I'd make a mast from a chunk of 1/2" copper water pipe. Look over Mark's instructions here.

http://www.qsl.net/k5lxp/mobile/HFMast/HFMast.html

Mark's a frequent contributor to eham.net and the rest of his site is very interesting as well. How many folks do you know who have built their own electric pickup truck? Making the mast isn't as interesting, but just about as well planned.

Alan, KØBG
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K0BG
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« Reply #2 on: June 02, 2003, 05:40:22 PM »

As I rethink this a little...

You didn't state which rig you were using mobile. But if you are using an Icom 706, and if your fiberglass RV has an aluminum ladder, you could use the ladder and an AH-4 auto-tuner. One enterprising RVer published an article in the ARRL Antenna Compendium (number 7 as I recall) detailing how he did this. Sure beat getting out and changing coils and makes things a little more stealthy in the process.

Alan, KØBG
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WB0AXN
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« Reply #3 on: June 02, 2003, 07:00:12 PM »

Alan wrote:

You didn't state which rig you were using mobile. But if you are using an Icom 706, and if your fiberglass RV has an aluminum ladder, you could use the ladder and an AH-4 auto-tuner. One enterprising RVer published an article in the ARRL Antenna Compendium (number 7 as I recall) detailing how he did this. Sure beat getting out and changing coils and makes things a little more stealthy in the process.

Hi Alan,

I'll be using the Icom 706, but hope to have the Hustler antennas tuned correctly.  I may try using a long wire with a manual tuner, if I get a good spot at a campground.   Per your suggestion,  I may try loading the aluminum ladder, since it's not grounded, that I know of.  (poor English here)  
Roland
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WB0AXN
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« Reply #4 on: June 02, 2003, 07:03:33 PM »

Alan wrote:

If it were mine, I'd make a mast from a chunk of 1/2" copper water pipe. Look over Mark's instructions here.

http://www.qsl.net/k5lxp/mobile/HFMast/HFMast.html

Hi Alan,

Wow!!  This is exactly the info I wanted!   Thanks a bunch, Alan.  Very much appreciated.   I'm handy enough to make something like this and I'm sure it will work perfectly.
Best 73's to you!
Roland
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KL7IPV
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« Reply #5 on: June 03, 2003, 01:57:46 AM »

I have had a 4BTV and a 5BTV mounted on my 5th wheel trailers by mounting a 1 1/2 inch pipe on the ladder rack. I allowed about 1 foot of pipe to protrude above the top of the ladder and mounted the vertical ant there. I used a MFJ tuner and worked all over the US that way. It was a matter of fastening and unfastening the lower coil clamps on the pipe when used. I tried to keep the top of the pipe as close to the top of the vents or lower just to keep the overall vehicle heighth below 12 feet. I broke the antennas down to 4 or 5 pieces that measured about 4 - 5 feet each and stored them in the side bins when traveling. Good luck.
73
Frank
KL7IPV
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WB0AXN
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« Reply #6 on: June 03, 2003, 08:35:12 AM »

Thanks Frank......for posting your vertical antenna setup using the ladder.  

Roland
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K0BG
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« Reply #7 on: June 03, 2003, 09:05:14 AM »

Roland, that stealth RV ladder antenna was in the ARRL Antenna Compendium Number 7, on page 84. The author is Jack Schuster, W1WEF, of 408 Thompson St., Glastonbury, CT 06033. Yor local library may have a copy, but you can buy in on-line from the ARRL too. This particular volume have several good mobile antenna articles and is a good one to own.

Alan, KØBG
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KL7IPV
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« Reply #8 on: June 03, 2003, 06:50:55 PM »

Roland, I also forgot the obvious choice...the plate type bracket that allows you to park a vehicle tire on it so hold a vertical mast for an antenna. I have seen them advertized in QST and CQ I think. They are a plate of about two feet by  one foot with a pipe welded to it vertically and then braced with some steel welded at angles to the plate. Use 1/4 inch steel plating and a heavy duty pipe to support the weight of the mast and antenna. You drive onto the plate and place the mast in the pipe and you are set to go. Good luck.
73
Frank
KL7IPV
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KA5S
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« Reply #9 on: June 15, 2003, 11:16:42 PM »

RV's are a challenge. I've always believed antennas should be high and in the clear. But if you can only go to 13 1/2 feet, and you START at ten feet, where the roof is on my Class-A RV, you have to get creative.

I've just mounted a modified, Superantennas MP-2 miniature, screwdriver-type antenna on a 33-year-old Pace Arrow. This is a mostly aluminum-skinned vehicle, with only the front shell fiberglass. I reduced the height of the antenna by replacing the whip with a top-hat made of three Radio Shack 40 inch replacement whips on a Hustler multiple-coil bracket, bent so they were almost horizontal.  Then I screwed a heavier L-shaped bracket to the metal just behind and above the driving compartment, allowing the antenna above the spring (an Outbacker base assembly) to clear the roof. The top-hat tips are at almost exactly 13 1/2 feet.  I also replaced the Superantennas-supplied mobile mast with a solid mast 20 inches long (M2's mast for a 2-meter HO loop) with steel 5/8 X 28 threaded studs. This is more rugged than the orginal mast. (A short Hustler mast will work, but is longer, and would raise the antenna higher than I want to go.)

The result is an antenna covering from below 7 MHz, on a mount which remains vertical until above 50 mph, and which is resilient enough (I hope) to avoid damaging the vehicle if I hit a low branch. On the air, I was running 5 watts today when I received a 549 report from a a 599 station running 40 watts. When I increased power to the same level he gave me an S9 report as well. This is a crude measure, but it shows that an antenna only 4 feet long CAN work on 40, on an RV.

Oh, that fiberglass front shell? Thank God and Yaasu for a good noise-blanker!

Cortland
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KA0GKT
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« Reply #10 on: June 19, 2003, 12:42:57 AM »

There was an artical about a mobile antenna called the Carolina Shorthorn in QST a few years (Decades?) back.

I have thought a person could use multiple Hustler resonaters along the length of the "Shorthorn".  The ground (more correctly counterpoise) can be  made with adhesive and copper foil the length of the fibreglass roof under and on the sides of the antenna.

Keep the antenna lower than the top of your air conditioner unit and you should be Okay...unless you regularly have to visit Coleman for a new A/C unit to replace the one destroyed by the low overpass ;-)

73!

de KA0GKT/7
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KA5S
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Posts: 229




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« Reply #11 on: June 19, 2003, 01:21:16 AM »

You know, I realized none of us have actually answered your QUESTION.

Yes, you can extend masts.  I've been collecting mobile masts and pieces of masts for years, adn I keep my eyes open for 'em.  Hustler sells a short mast, which may be used as an extension by putting a 3/8 X 24 threaded coupling on the top.  Some mobile masts have female threads on both ends, and a 3/8 X 24 set screw, a piece of 3/8 X 24 stock, or a bolt with the head cut off may be used on one end to extend a too-short mast.  M-squared sells a mag-mount with 40 inch or 20 inch masts to hold their HO-loop antennas, and these also are servicable masts or extensions for HF antennas. However, I'd not recommend soft aluminum masts male threaded 3/8 X 24; the threads tend to come apart inside the (usually steel) mounting hardware.

Today I mounted a DK-3 screwdriver antenna horizontally on the aluminum roof of my Class A. I put the feedpoint end on a single 5 inch magnet stuck on a galvanized metal tile (which holds an MFJ dual band antenna, too) held to the aluminum roof with silicon adhesive tape.  GROUND is a strap to a part of the (metal) roof with a beam under it, and a good, tight, weatherproofed screwed-down lug -- and  breakable wire.  Another tile will go on the front tomorrow when I find the roll of tape or buy antother one, to keep the antenna oriented fore and aft. It sticks forward over the driver, where the roof is fiberglass.

Using magnets, and nothing really strong holding it to the roof, it can slide off without, I hope, making holes in the roof if I hit something low.

If the roof were ALL fiberglass, I'd not be so concerned with location, but I'd also not have such a good counterpoise. Seems to me, you could mount a Hustler similarly to what I've done, and use metal tape for a counterpoise.


Cortland
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KA5S
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« Reply #12 on: July 03, 2003, 12:11:13 PM »

A followup:

Trying to keep the antenna low and still get 80 and 60 meter operation, I mounted a DK3 Screwdriver antenna horizontal on the roof, pointing forward, with its capacity hat just in front of the cab. The antenna is over fiberglass, while the feedpoint is over aluminum. Predicably, this turns out to not work as well as it could: There are running-light wires right below the antenna. Last night on 60 meters, the *dash lights* came on as I spoke, from induced current.

Back to side mounting for that one!

Cortland
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KD4EDE
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« Reply #13 on: October 18, 2003, 01:45:33 AM »

FWIW.  I once saw a motorhome, with a metal luggage rack on the roof, that had different Hustler resonators mounted on each corner of the Square rack.
 The rack covered the rear half of the motor home roof.
 The resonators coils were somehow mounted directly  to the roof rack railing without any mast.
  I'm not sure how well it worked.....or how it was tuned, but seemed like a solution!  I'm guessing the rack was loaded up as a whole...and the resonators tuned for each band they wanted to work.
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WA6CDE
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« Reply #14 on: December 05, 2004, 11:33:18 PM »

I was asked if I could comment on this subject from the 4/5/6 btv thread...

First off my experance with extending the shaft whip section of the hustlers resonators will not work... it changes the charistics completely... their system is made for so much below.. the resonator... and then so much above... and thus not recomended... you go changeing the length of the bottom section...

If your dead set on using them... then one has to build a stronger base up to where the ball/spring/shaft setction starts..  

I would not use copper tubing... its too weak... and once it goes.. its going to break off... it was made for internal water pressure.. not bending stresses.  

Your idea of using the bumper is good... but, I would go this route...which makes it much more useable for a couple of antennas...

(hustler mobile resonators are at best not very efficent.. while they work... their are better antennas which can be used.)

What I would do is go get a 2x2 hitch reciver welded to the cross member.. or else a bolt /welded tow bar... that way you can use it to tow the boat or car later if you like...

then I would find a piece of 2x2 x 0.2 (almost a 1/4 inch thick squair steel tubing...   which will fit into the reciever... drill a pin hole to hold it in... to this tube weld a piece of 1-3/4 x 0.20 wall squair steel tubing what ever height you are going to... (about 6 ft is almost max... remember you have to reach the resonators or the fold over part of the mast to change them) on the top side of the vert tube... have weled a piece of 5 inch dia x 1-3/4 wide x 0.2 round steel tubing...(not water pipe)  which will become the base  for the ball mount... in a vertical position... on one side of this 5 inch tube ... skip weld a piece of 1/8 inch plate for mount the ball and its backing plate... you will have to drill the holes as required to mount the ball mount and its spring... may I suggest the Hustler.. super stainless steel ball mount and heavy duity spring... comes complete (ball, spring and plate for about 50 bucks) if you want it to last.. stay away form the radio shack or the cheep cast ball mounts...  the heavy duity one from hustlers.. is the old motorola mount re-made today... and they will last a lifetime.. where as the others are pretty flimsy and cheap... (no I wouldn't go get the AH-2b either... not for what they want for it... ouch...  

that should take care of the moble mounts... now why the trailer hitch reciever...

Well when your parked for a while.. you can remove the moble mount easly by removing the tube inserted into the reciver... un-screw the coax from the mount.. and remove...

Then....

Take another piece of 2x2 that will go back into the trailer hitch reciever... (again drill for the holding pin...  Except this time instead of welding the 1-3/4 squair tube on... weld a piece of 2-1/4 round tubing... that is about as thick as the 1-3/4 squair stuff... again you can make it any height you want... but, I would stay around the 5-6 ft range again... as the longer it is.. the more clumbersom it will become to store...

Why the 2-1/4 inch tube.. well thats so you can put the hustler 4/5/6 btv on the back... and have a much better antenna when your parked for a while... some regular old electrical wire... for radials... I use some yellow No. 12.. but, anything will work... and try and get the somewhat arranged out steight.. if not... do the best you can... getting a good ground to the water pipe or something... These can be attached to the back bumper or the new 2x2 tube which goes into the reciever on the hitch... I used some electrical grounding lugs.. made out of copper... sold in electrical supply houses... and have a screw in them to hold on to any wire... 1 or more... that way all you need is a screwdriver to put out the radials...

Now if you wanted to get real fancy... you can sub the round tube (2-1/4)  for  1-3/4 or 2 inch...square tubing that will fit the base mount for the 4/5/6 btv  ... all the way to where the base is at the top of the motorhome or trailer... and you can attach a permanate wire/flat tape or copper strip.. to the roof.. ( I would ground this to the RV frame also so it will work for the mobile mount too)  and if your motorhome/trailer/rv is 30 ft or longer... your in luck.. for a natural ground plane base... least one side... for 40, 30,20,17,10 meters...  and if you cut the mast tube you can use two straps of 1/4 inch x 1-3/4..etc.. one.. on each side.. with two 3/8 bolt spaced out on each side of the tube split... to bridge the cut.. hint... drill and put the two side plates on first .. then cut the tube in the center distance between the inboard bolts.... then...by removing one of them on the top side the 4/5/6 btv will fold over  on top of the RV... once your spider hat assembly has the fold back modifications...  need to adjust it... fold it backwards and you can work on it from the ground... control of the antenna is accomplished by going up the ladder and walking it up ... then dropping the bolt into place which will lock it up...  also in the stored position.. make sure it has a storage lock... so it won't fly up while your going down the road...

With this system you can change antennas and have the best of both worlds...

but, again this is just a suggestion and not plans to build it... we started the idea... but, that was written by someone else and published in QST for the airstreams... but, this is my current design also... for my RV...

Oh ya the folding back spider assembly... get some longer brass screws... and a bunch of brass washers... and some nlylock nuts... and some springs... yes you can buy springs in hardware stores... the compressive type that are just a little bigger than the screws... put the screw through a washer... then through the spring.. another washer.. the tube.. the spider plate.. another washer and the nlyock nut... now the spring will hold the tubing down in the spider mounting plate.. but, it will allow it to cam back out so you can fold them back out of the way...  

Hope this helps.. WA6CDE.. 73
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