|PAR (LNR Precision) End Fed Half Wave Antenna... My experiences with the
Par 20 meter EFHWA and my own 10 meter version that Im building up to try
out. (I guess I can call my own homebrew version: A Par-style EFHWA.
Snooping around the world wide web with search engines.. I have found a couple of
articles and a series of pictures (on Flickr) that pretty well disclose how the PAR end fed
have wave antenna is made. Someone actually cut the matchbox with a saw or dremel
tool and opened up the 20 meter version.
It is somewhat different than most if not all the other end fed half wave circuits. The
inductor is not tapped for a 50 ohm feed. VERY VERY interesting. I think someone must
have done some homework on this matchbox. It works pretty good. If you check the
eham reviews the reviews are excellent. I went out and bought a PAR 20 meter version in
October. The shipping (up here to Canada) was about $25 which adds to the cost of the
antenna significantly. I ordered the 300 watt version.
The swr curve very much resembles what a standard half wave center fed dipole would
So far Ive been mostly listening with it. I plan to try it out during some qrp cw contests
later this fall and at the same time..compare it with my backyard vertical. On receive..the
vertical in the backyard is about the same or sometimes better on stateside signals..but
the orientation of the PAR efhwa is sloping off the tower and is more favouring the USSR
that anywhere else!!! Still..it seems to work fairly well. More antenna work is to be done
I plan to raise the far end of the Par efhwa so that it is more like a horizontal dipole facing
Here I am starting with a sketch and some junk
box parts. The coil measures about 1.9 uh on my
L meter. That is about 1/2 of what the 20 meter
coil I wound on a T80-2 toroid (26 turns nr 22
This is according to the flickr pictures of a cut
open 20 meter match box.
The sketch (pictured left) is from another
internet site. It shows a 20 meter end fed match
box. I wonder if they got this idea from the flickr
As I say later in the article..I have been looking
over the EFHWA web sites (homebrewing) and
they all have a type of tank circuit that is tapped
for a low impedance feed. This "Par Style"
antenna is a bit different. No low impedance tap.
10 meters has been HOT lately this fall. So much
so..that I have suspended experimentation on
the 20 meter version I had built. I was going to
box up my 20 meter homebrew EFHWA match
circuit and then carefully compare it to the 20
meter PAR EF-20 that I have purchased from the
manufacturer. I .. WAS.. going to do a careful
analysis on the bench and up on the
tower..BUT..since the sunspot cycle seems to
have "suddenly" switched into high gear..
I am going to work on a 10 meter version.
The air wound coil in the picture was my first
thought..but the lead wire broke on the coil so I
searched the junk box and found a number of
tightly wound air core coils made from
enamelled wire. They measured about 1.85 uh or
so. A little less than I would have liked..but
..with the lead lengths involved in hooking the
coil up..I figure it might just work fine. The hook
up leads would probably account for a bit of
inductance in the circuit as well.
Below: quite a bit of searching yielded a schematic of what looks to be the innards of a Par EF-20 (End Fed Half Wave Antenna or EFHWA).
The coil I planned on using broke. Must have had a nick
in the wire. So I looked in the junk box and I found some
of these wire coils that were tight wound with enameled
wire. Measured 1.846 uh on my LC meter from HONG
KONG I bought on ebay. NOTE: I have not actually
verified just how accurate (or inaccurate) this meter is
(YET)..but it gives me a definite reading to three decimal
points and I presume if it is out by a certain amount..that
it is a repeating error and at least..it gives me something
to go on.
I would have rather had 1.9 uh or about 1/2 the value of
inductance that I measured with the T80 toroid and 26
turns of enamelled wire.
With the longish lead lengths I am using in my plastic box
to enclose the circuit..I figure there will be some stray
inductance ..so I went and tried this coil in my test circuit.
Above a T80-2 with 13 turns. The spacing of the turns changes the inductance
quite a bit. The windings would have to be set in Q Dope to be stable.
The -2 material is supposedly useful up to 30 mhz but mostly for circuits above 14
mhz a yellow -6 material is used. Since I had no T80-6s in my collection..I decided to
go with the air wound core coil.
I used a ceramic standoff glued to the box as a mounting point for the antenna
end of the coil.
If one wanted to..he/she could use a smaller box. This one I have is about the
smallest one in my plastic box collection. It is a kind of soft plastic and maybe
not as rugged as I would like. But, I will use it. I will seal the lid with gasket
sealer and I will making the box more rugged with protective layers of
electrical tape to keep the sun off the box and keep our harsh northern
Ontario weather from penetrating it.
Above..the circuitry is wired up for a test outdoors later today. It is sunny and slightly
below freezing today and just a tiny bit of snow on the lawn. Good antenna
experimentation weather!!! I have closed up the cottage for the year and put the boat
and fishing tackle away (November 17th 2011). I used brass bolts and copper
plumbing strap (available at most hardware stores. I used about 3 inches or so of nr
14 bare copper wire to make a line from the antenna bolt connection to the ceramic
post and a bit beyond that to allow for the coax capacitor to be joined easily.
This 3 inches of wire will probably become part of the antenna itself.
The coax capacitor is 5 inches of RG174 type coax (Jacket intact)
with an additional .75 inches rougly that the jacket was stripped away and the braid
separated and tinned and the center conductor tinned ready for connection to the
circuit. Total inductance measured 11.70 pf on my test jig.
|click here to go to page 2 of this
article..where..November 17th 2011 ..I go outside and put
this homebrew 10 meter matchbox with about 16.5 feet
of wire part way up the tower and test it with the MFJ
antenna analyser.......>>>>>>NEXT PAGE LINK
NOVEMBER 2011 Project.
link to the home page ve3ab at
bottom of this page.
Update (12 Nov 2013)-->> The antennas today: PAR EF-20H, a PAR EF 40-20-10 .
These two antennas are up about 40 ft or so and they slope down off the tower.
ALSO ..I have a Jetstream JTV-680 vertical that Im trying out. A 2 meter dipole is
also in the picture part way down the tower.
|The 40-20-10 meter par..slopes off the top of the mast towards Europe more or less. The 20 meter EF 20 goes the
opposite direction and maybe a bit north of west.
The JTV 680 is seen parallel to the tower. I tested the JTV 680 vs. the 20 meter sloper to a western Station out in BC (VE7
land). The 20 meter sloper (.5 wave) was 3 to 4 S units better than the Jetstream Antenna. ---> Mind you..the JTV680 was in
a different location in the yard and lower to the ground during this test.
I then decided to move the JTV 680 up away from the ground to help its performance. On 80..it is weak compared to other
stations in town here (checking into the Laurentian Net 3.755 mhz ssb. The other in town stations were good solid copy
whereas I was barely audible at a 100 mile path and the net controller a few hundred miles away..did not copy me when I
tried checking in.