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HF Reel Type Portable Antenna for QRP

from Marvin Hamilton, K9GDV on December 10, 2017
View comments about this article!

"Editor's Note: Due to the popularity of some of eHam's older articles, many of which you may not have read, the eHam.net team has decided to rerun some of the best articles that we have received since eHam's inception. These articles will be reprinted to add to the quality of eHam's content and in a show of appreciation to the authors of these articles." This article was originally published on: 04/09/2004





An HF “Reel Type” Half Wave Dipole Antenna for Portable Low Power Use

(Or A Poor Man's Tape Dipole)

by K9GDV

My original madness

As most of us that have gotten bit by the “portable” or “qrp” bug in recent years, I have tried a variety of the “off the shelf -portable” antenna's to different degree's of success. The “old standby” half-wave dipole, very hard to beat. As it is the “old work horse” for dependable operation.

Some of the “Off the shelf“ portable antennas seem to work well, but have their limitations. Since acquiring several low power rigs, (the latest being the Icom 703 plus) I wanted to have a portable dipole antenna that could be used with a low power rig, and have the ability to cover more than one band, without carrying too many parts & pieces to get lost.

Some of you will remember the factory made tape dipoles that were produced by Hygain, or Collins that were easy to field deploy and carry. Tape dipoles could be setup for the desired frequency by pulling out the tape to the proper length and hanging them up. They are rather rare item now, as they haven't been produced for several years.

The Army had an antenna for the PRC-77 that used a Fly fishing reel to hold the wire, designated as an AT-984/G. Having recently seen one of them planted a seed in my mind. My usual portable dipole antenna consisted of coax cable, center insulator, and several pre tuned rolls of antenna wire for whatever band I chose to use. This was a bit awkward, due to numerous items to be carried. It would be nice to have a single package half wave dipole antenna that could be used on multiple bands, without carrying separate roll of antenna wire for each desired band, have the guy ropes and support rope all as one item, plus permanent frequency markers on the wire for desired bands.

0x08 graphic

How to mark the antenna wire, with a permanent non-slip marker, so that fairly dependable frequency repeatability could be obtained? I found that non-insulated metal ferrules, available from Digi Key, slid over antenna wire during assembly and later crimped into place during tuning of the antenna, when desired antenna resonance point was located, would provide a permanent marker, and wouldn`t slip. Fair Radio Sales has surplus Dipole antenna fixture (Originally for a PRC-74 by Hughes) that would do as the center insulator and main body for this project. Next thing found from Wal Wart was the Martin Model 61 reels (Chinese made inexpensive ones) They slid over the Dipole fixture frame perfectly. Just remove the 4 screws that retain the reel plastic mounting foot, and discard the plastic foot. To mount reels to the frame hold reel and dipole frame together, (look on face side of inner ring on reel - where bobbin fits- and insure that you don't have reel assembly slid too far in towards frame rail, or you won't be able to reinstall the bobbin onto reel assembly.) Then align and use the 2 existing holes on reel to mark dipole fixture, center punch and drill holes completely through fixture for a #6 x 1-¼ machine screw and mount reel to fixture.

I used surplus “push terminal” connectors, but one could use brass machine screws and wing nuts instead (use 10-24 threads) These are the dipole feed line to antenna wire connectors. (The push connectors also were from Fair Radio Sales and have a good grip and won't allow antenna wire to slip.)

0x08 graphic

25 feet of RG-174 coax cable was used to replace the original 72-ohm twin lead that comes with the Dipole fixture from Fair Radio. (Yes- it has some loss.)

The Reel bobbins will hold about 36 feet per reel of #14 gauge flex weave wire, so you will probably have to settle for 40 meters as the lowest operating frequency, rather than 80 meters, which can be obtained if using a smaller gauge of antenna wire. (Fair Radio also has small quantity of bare Phosphor Bronze “Gibson Girl” antenna wire in approximately 300 ft reel, which may be a bit tangled up-if you are fortunate enough to get some of this wire the two fishing reels will hold enough of this wire to operate down to 160 meters) I used Fishing Snap swivels on ends of the antenna wire for quick connection to the PVC pipe insulators on the support ropes. Before attaching snap swivels to ends of antenna wire stack 9 to 15 ferrules on each antenna wire to crimp at resonant frequency point during initial tuning of antenna

.

Tuning antenna

Measure out the length of wire, as calculated for half wave antenna, for the desired lowest frequency as a starting point and then use an SWR HF antenna analyzer, or SWR wattmeter and your transmitter to “tweak” the antenna to the desired resonant frequency. Be sure to begin at the lowest frequency you wish the antenna to operate (maximum antenna wire extended) at and work your way higher in frequency from there. Once you have the antenna tweaked” to the selected frequency, slide a ferrule up to the point of contact of the antenna wire and the dipole terminal connection, and crimp it in place. (One for each terminal connection) Then proceed to the next desired higher frequency and repeat the operation. After finishing placing the marker ferrules on the antenna wire you can pull out the antenna wire to the appropriate frequency marker ferrule, place the antenna wire in the terminal connector, and have a fairly accurate repeatability for resonance at the selected frequency. (Resonance point may vary a bit, from either side of crimped ferrule marker, depending on different installations of antenna height and soil conditions ) Oh! You better write down what frequencies you have placed ferrule markers at and keep list with antenna. (May want to color code ferrules also with DOB's of various colored paint)

If you use small size antenna wire, this antenna should only be supported using the center insulator, (Inverted “V”) as the wire may not be strong enough to hold up the entire arrangement. (#14 size wire should not be problem).

The next Reel dipole antenna I'll try adding a small, lower power 1:1 balun to it and see how that works.

The coax, support ropes and antenna wire are all carried on the Dipole “H“ frame center insulator, as one item, instead of separate pieces, which was one of my objectives in this project. To use the “reel” dipole, unwind the support ropes & coax from the dipole frame and reel off the amount of antenna wire to the ferrule marker of the band you wish to operate on, attach the antenna wire into the “connector” terminal, pull up the dipole frame center insulator to desired height in tree, or other support, string out dipole legs and tie off ends, hook up coax to transceiver and you are ready to go on air.

0x08 graphic
9

On air tests were run on 40 meter SSB, 20 Meter PSK and 17 Meter SSB using an Icom 703 plus at 5 watts and 10 watts. With resonate dipole the built in antenna tuner was not needed. As with any dipole, the frequency can go +/- of the center frequency somewhat without SWR going to high. No comparisons were made to other dipole antennas. This antenna was initially tuned as an Inverted “V” with center insulator relatively low to the ground. (15 to 20 feet) Ends of dipole were about 2 to 4 feet above ground. I suspect in this configuration there may be some NVIS antenna characteristics involved, as stations contacted on 40 meters were 100 to 500 miles away, and they gave me a decent signal report. On 17 meters stations several hundred to 1000+ miles away reported good signals and the same applied to 20 meter PSK.

The “Reel” dipole was not designed for permanent installations, but you should have no problems with it if left up for short period of time, such as field day, or even for a week. If you are true backpacker, the #14 Flex weave wire is a bit heavy and you will probably look for smaller gauge wire, to lighten the load a bit. Maybe you'll find a use for the 75-ohm twin lead that comes with the Surplus Dipole fixture, instead of using the RG-174 coax.

So let your imagination guide you, and you can probably come up with a some sort of other ideas for use of fly fishing reels for an antenna that will fill your portable requirements.

Fair Radio Sales in Lima, Ohio. Dipole fixture Fair Cat. # DP-MK-911; Terminal panel Fair Cat # TP-10 (has 10 each Heavy duty push terminals); CRT-3 Gibson Girl wire, Fair says they have few left, but tangled wire.; Martin Model 61 reels were obtained from Wal-Mart, but are also available from sources on the internet.; Brass machine screws, finishing washers, and thumb nuts can be used in place of the surplus push connectors to clamp the antenna wire and can be found at your local hardware store.; Radio Works has the .070 black Kevlar 500 lb test rope.; Digi-key has pre made non insulated ferrules. The P/N's used in this project are: For # 20 wire as marker 288-1085-ND; For # 20 wire looped upon itself ferrule used as retainer 288-1090-ND; For # 14 Flex weave as marker 288-1105-ND; For # 14 wire looped upon itself ferrule used as retainer 288-1110-ND

Member Comments:
Add A Comment
 
HF Reel Type Portable Antenna for QRP Reply
by K7NSW on December 10, 2017 Mail this to a friend!
A great idea and model to copy. One show stopper is the cost of a crimping tool to crimp the wire ferrules. The reference to Digikey takes you to the web page for American Electrical, Inc - the source for the wire ferrules. The crimper is pricy. I would like to know how the author crimped his ferrules. Did he buy a crimper?
 
RE: HF Reel Type Portable Antenna for QRP Reply
by N8AUC on December 10, 2017 Mail this to a friend!
This is beyond cool!
I need to build one of these!

73 de N8AUC
Eric
 
RE: HF Reel Type Portable Antenna for QRP Reply
by K0UA on December 10, 2017 Mail this to a friend!
You could easily crimp the ferrule with a pair of sidecutters . Just modulate your crush power to not cut the ferrule. I have crimped things for years with sidecutters.
 
HF Reel Type Portable Antenna for QRP Reply
by K0VH on December 11, 2017 Mail this to a friend!
This is a great idea, definitely built heavy duty and who doesn't like to homebrew antennas? For those who want a quick solution, google yo yo antenna and the one I got for Christmas 6 or 7 years ago to use with my (at the time) IC703 is still available. It's not near as fancy as the one shown in the article but easily fits in a backpack QRP setup and great if you are the "once a month in summer" QRP operator. 73 de SE MN
 
RE: HF Reel Type Portable Antenna for QRP Reply
by KB6QXM on December 13, 2017 Mail this to a friend!
This article is about QRP. With today's bad band conditions, the new definition of QRP is under a 1,000 watts.
 
HF Reel Type Portable Antenna for QRP Reply
by KK6ZSA on December 24, 2017 Mail this to a friend!
Now I know what I can do with my old fly fishing reel.


 
HF Reel Type Portable Antenna for QRP Reply
by KK6ZSA on December 24, 2017 Mail this to a friend!
Check out the larger fly fishing reels for heavier weight fly lines. Reels designed for salmon, steelhead or saltwater fishing will probably do. They are larger and will accommodate more wire.
 
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