R7 Vertical: MODIFICATIONs, notes and ideas
hamelectronicsmagazine.com for March 2011
For Field Day, 2005, I operated in the backyard by the lake and I built a 20
meter monoband vertical using parts from an old R7 vertical. I bought the
R7 Black Box for $5 at a flea market! What a deal!!! The R5 and R7 black
boxes are not all that much of a secret anymore. Several internet sites
have the schematic and some information on how to build one. In
particular..EI7BA has a pretty good homebrew version of the black box he
built pictured on his web site.
The R7 vertical is not really a half wave vertical as such but more like a
shortened half wave vertical with some sort of capacity hat on the bottom.
Not sure (exactly) how it works..but if I were to build a monoband version
for the various bands...
a 12 to 13 ft vertical element would probably be about right for 10 meters.
A 24 to 26 ft high vertical element would work for 20. I built this one for 20
meters and I did not use a full 24 feet but a bit less than that and I used
some helical loading (about 10 ft of copper plumbing strap on a fiberglass
pole then I used aluminum tubing from an old vertical for the top part of
For radials..I used pieces of aluminum tubing and hoseclamped the whole
thing together as a LASHED UP VERTICAL for 20 meters.
It was field day afterall!!! I suppose..this could simulate an exercise where
all my antennas blew down in a high wind or ice storm (we did have a bad
ice storm January 1998 and our hydro was out for almost 2 weeks).
Anyways..this lashup would simulate me picking up some aluminum tubing
and lashing it together quickly to form a good radiator. For emergency
power..I used the battery from my Ford Truck and I operated from the
PIcnic Table close by or ..at night..I went into the metal garden shed.
Anyways..it was an interesting exercise building this antenna. I plan to
rebuild it again ..only trying some new wrinkles. How about a 30 meter R7
or a comprimise length that would work on both 20 meters and 17 meters
with reasonable SWR.
The latter would be very possible due to the fact that this antenna was
very FLAT in SWR and could be made even more broadbanded using
perhaps thicker antenna elements.
I'm going a bit from memory and the pictures arent that clear but the swr points from 13.631 to 14.517 were about 1.5 to 1 and very flat
across this almost 1 full mhz. This with the fact that the vertical antenna was not even completely full size..seems to indicate that it is
very broadbanded. I think a 14 mhz antenna might even work reasonably well on 17 meters without traps or stubs or anything. Would
be a bit large though for the top of a tower! --- I'm thinking for Field Day 2011..comming up this spring..I will take down the Butternut
HF2V in my back yard and I may try this R7 in its place. I would make it so I could adjust the length so that I could operate all the high
bands 20 meters through 10 and maybe even 6 if the R7 would work on 6. Not sure about this.
links to web sites featuring R5 or R7
This one is for the R5. Good pictures and text. Links on this
page to the EI7BA web site and this person rebuilt/built the
"black box" using information from EI7BA.
My Black Box was fine and did not need any work on it. You
can build one from scratch but you can also pick up one of
these antennas used and rebuild or just clean it up.
A couple of important notes: critical dimension..where the
bottom piece of the vertical goes into the insulator. From
what I hear..if the base piece (aluminum) goes too far into
the insulator..you will get all kinds of screwy swr readings.
In my case...and I think in EI7BAs instance...I used a
fiberglass pole at the base of the vertical (green in color).
It was a pruning tool for pruning branches of trees. A
fiberglass shovel or rake handle might do as well..just cut
off the unwanted parts. This makes it easy to interface and
makes the mechanical assembly easier.
I used a 10 ft length of copper plumbing strap wound
helically up the fiberglass piece..gave it some inductive
loading and then I interfaced with a small slug tuned coil.
That is an easy to build unit actually. I just took a common
glue stick and some torroid cores that fit inside it. I stacked
some -6 cores..I think they were T106-6s or perhaps
T130-6s. There were five or six or so glued together in a
stack. Then I took about 4 turns of common aluminum
ground wire and made a makeshift coil that would be tuned
by this gluestick coil (manually) like a lipstick or chapstick.
What this did..is give me some way of quickly tuning this
vertical antenna. It was FIELD DAY..2005. A simulated
emergency situation. I was using a lashup vertical and I
wanted to get on the air quickly and I did not have time to
cut and prune the antenna. As it turned out..this antenna is
very very broadbanded and quite forgiving ..as I found out.
Perhaps..a suitable glue stick style inductor or roller
inductor interface..might allow tuning on multiple bands.
Another option..wire elements with a fiberglass mast.
Parallel elements run up and perhaps off in INVERTED L
type of configuration.
A good Field Day antenna I would think. Easily
moved..deployable. I can see a portable tripod made of
lumber or perhaps just a log in the ground or something.
The R7/R5 is supposed to be at least 5 or 6 ft or so off the
ground. Ground mounting it ..I dont think..would work too
Getting it as high in the air as possible..in the clear..would
be another good idea. maybe up on a rooftop...hilltop or
Above the glue stick tuning mechanism. Permeability tuning. Using yellow or red
cores "approximately" doubles the inductance of the coil. In the antenna above:
with only 4 turns of coil..this is what I would call a "tweaker coil". YOu could move
the resonance of the antenna a wee bit in one band with that.
For multiband/field portable use/field day..you could use a bigger coil and
perhaps have a special test lead to short out the coil completely..or perhaps a
wandering lead coil (like the outbacker antenna)...many possibilties exist.
This vertical..while being less than a full half wave on 20
meters was still pretty large at about over 24 ft overall
height. I'm going by memory. SWR was flat all over 20 and
Field Day..and/or Field Deployable Antenna Ideas for this "type" of vertical are discussed.
These days..quite a few QRPers are venturing out in the Field to operate. Just look at YOU TUBE videos of people out on shorelines with MIRACLE
WHIP verticals and QRP rigs or portable dipoles. Today..I read on QRP-L, (I have subscribed to this list since the late 90s)..one fellow was going out
to a park (WR0W). with an HW7. Doug Demaw went to the Carribean with his modified HW7 back in the 70s and I read that article a few times and
sounded like a real neat adventure. I tried back in the early 80s to build his receiver circuit..but didnt get it working back then. I have all the parts
now and several HW7s to play with..perhaps I will try it. Anyways..backpacking with FT817s or IC703s or MFJ rigs is common these days. I'm tempted
to try it myself. Im tempted to take my rig out on a my aluminum boat while fishing. The boat would be the ground plane and I would use a vertical
mounted on the front. When I go out portable operating..with a portable QRP rig..my idea of a field deployable vertical would be "perhaps" a R5 or
R7 style vertical with counterpoise spokes that perhaps telescope out and an adjustable radiatiing element of some sort. I suppose it would have
to be lashed up to a post or something.
On land..this R7 type antenna would work..on a boat..would be not as easy.
More to be written soon...March 15, 2011. Tommorrow supposed to be a real nice weather day with sun and above normal temps. I may set my R7
prototype up outside and lash it together for fun and try it perhaps on 15 meters. The higher bands are perking up! A mono band R7 style vertical
would be (about) 19 ft long or thereabouts. I think I might have a suitable aluminum radiator about that long. Perhaps that aluminum tubing golf ball
retiriever that I bought at the thrft shop could be tried. It collapses and expands out quite a ways. 73 for now..and watch for more on this site as it
MY OLD SITE www.earlandrews dot com has plenty of pictures of this Field Day antenna used in 2005. I lashed it up in a hurry...but ..hey..that is
what FIELD DAY is all about. ..you simulate an emergency where the antennas have to be lashed up in a hurry and your station put on the air as
quickly as possible and with emergency power..out of doors.
IF you google R7 and or R5 and the
words "rebuilding" or something
to that affect..you will get all kinds
Here is a diagram of a circuit board
I found in a pdf file. Far Circuits in
USA was making this circuit board
for repair of the R5 or R7 vertical
You could use it to "roll your own"
homebrew version of course.
There are enough web sites with
schematics and pictures and
drawings that you can pretty well
get all the information you need.
As for traps..I don't want to use
them. Id rather use parallel wire
elements or maybe a screwdriver
mobile type coil with a fairly long
and large diameter aluminum tube
or even 2 inch 12 long copper pipe
that I would buy from HOME DEPOT
or something. Would make a nifty
backyard vertical..as long as it
didn't topple down on someone or
For a backyard
vertical..I would want the base of
the vertical up about 8 ft off the
ground supported on a sturdy post
or perhaps a single tower section.
That way ..you could walk under
the radial spokes.
Here is a picture of a balcony screwdriver adjustable
antenna that Ted VE3DXG built. I actually bought one of
Teds old screwdriver mobile antennas and I have started
rebuilding it with new wire and new fingerstock.
NOW..picture a 12 to 18 foot lower section matched with
the R7/R5 match box and the motor adjustable coil with
say a 6 or maybe 7 ft stinger above the coil.
This would be my idea of a good multiband remotely
adjustable vertical without traps that would tune from 40
meters through 10 meters continuous coverage.
Mechanically..it would take a bit of work and
experimentation. IF the first one foot of the vertical were
a fiberglass or PVC pipe of about 2 inch diameter then a 2
inch aluminum tube..the matchbox could bolt to the PVC
pipe or fiber- glass pipe and the radial ring could be
clamped on appropriately. There would be a wire to
fasten the feed point to the main vertical mast. That
would be my idea for a decent remotely tuned vertical
that would not require a massive ground system at all
and would be portable. Could be set up in the field.
I want to build this type of antenna and I may do it either
this year or next. Perhaps for Field Day.
The meter readings dont show up
in the photos..but the SWR was
very low from about 13.66 all the
way up to 14.517 (these are the 1.5
to 1 points) if I recall correctly.
OF course..the original R7 vertical
was not a mono bander!! Far from
it. It had traps for
10mhz,14,18,21,24 and 28 mhz. On
40 meters (7mhz) it was a loaded
March 30, 2011 -- Just a note on band conditions: 15 meters is opening up now. I guess we are seeing
improved conditions on 15. I read the other day on my QRP list (QRP-L) that 15 and 17 meters were
"hot". -- With the higher bands improving..these NO radial verticals could see use on the higher bands.
I "myself" dont like traps. I would be tempted to use the screwdriver mobile antenna with the R7 black
box to make a relatively efficient vertical that does not need ground radials. Another idea might be to
run parallel elements beside each other one for each band of interest to have multiband capability.
One question I saw on the various
forums on the web was..."will the R7
work on 80 meters??"
I (myself)-- would say..that ...the black
box circuit would have to be
modified..and of course the radiating
element would have to approach an
electrical half wave on 80 (probably
with a coil). The RFC seen on the
board would have to be at least 200
uh or so --otherwise it would create
losses on 80. I seem to remember
measuring it at 150 uh..(not sure
about that though!
I myself..was wondering if it would
work on 6 meters. Perhaps someone
will try it out and report it to me.
I did operate the modified R7 (modified for 20 meters monoband) on Field Day in 2005..but I was rather
busy with moving from Ottawa area up here to Elliot Lake..so I didnt have a great deal of time to
properly evaluate this antenna. To properly evaluate it..I would have to compare it directly against
another antenna in the same general location. All this takes time..and time I didn't have back then.
Perhaps I will get a chance to try it again. I'm thinking of using the R7 (modified for 15 and 10 meters)
for FIELD DAY 2011. I will build the antenna weeks ahead of FIELD DAY and try it out ahead of time. I will
compare it with reports to my other antenna ..which is a TGM MINI BEAM on a 30 ft tower. That should
give some good relative indication of the merit of both antennas.
I will post my results here on this page(s) and I will write up with plenty of pictures. So look for a follow
up on these pages in JULY 2011.
73 Earl VE3AB
IMPORTANT TIP: I bought an R5 off a swap net back about 10 years ago and after
putting the sections together..the SWR readings were horrible. The joints and the
fouled up bottom insultor had to be cleaned up big time. When I took a few hours of
scrubbing to do this..the SWR reading were fine. There are many joints and
connections in these verticals. They all need to be good. The insulator at the bottom
gets fouled. The radiating element cannot go into the insulator furthur than what it
was originally meant to do..otherwise the swr readings go wild!! I get around this
when I built my modified vertical ..by using a piece of fiberglass tubing at the base
then I run aluminum tubing as the element.
The EI7BA web site shows his "homebrew" black box and his
homebrew vertical. He too uses a section of fiberglass tubing
at the base. Makes it easier to build the vertical. He has some
good links to TRAP REPAIR.
HERE ARE SOME PICTURES OF THE R7 VERTICAL USED ON FIELD DAY 2005
I LASHED THE ANTENNA TOGETHER RATHER QUICKLY WITH HOSE CLAMPS
AND PIECES OF ALUMINUM. The base of the vertical is from an old vertical
antenna and the green fiberglass tube is from a garden tool. The fiberglass
pole makes it easier to attach the radial spokes-- (they are not at "coax ground
potential" and I used copper plumbing strap in a helical coil. THIS WAS A LONG
VERTICAL MONOBANDER FOR 20 METERS. A quicky vertical lashed up for
field day..emergency simulation. A more rugged and better built version would
be a very interesting monoband vertical or perhaps multiband. This antenna
had a very broadbanded characteristic.
I mounted this antenna on the back of my truck. I used the trucks battery to power my radio. I
was moving at the time..(2005) and did not have the time to really work a whole lot of
stations but I did work some on 20 meters. It took a few hours to gather the part and lash
them up to make this antenna.
For a temporary Field Day antenna..this worked. For more permanent use..stronger
construction would be required ..but the basic ideas and material types are useful for
experimenters to gather their own ideas.
Field Day 2011 is comming in June. I plan to
resurrect this antenna and build a similar one for
use this field day. Perhaps a dual band 15 and 10
meter version. I will publish the article in July this
year. please check back then..73 earl ve3ab
thumbnail picture..click on it to
expand to full size and then
escape button to return to this
Above sketch. This is the antenna I want to build for
field use. A motorized..or non motorized adjustable
vertical with the R7 black box. up on a pole above
ground so that I can walk under the radials.
It would be nice to have the antenna on a pivot so that it
could be folded down for adjustments and for when bad
storms are in the area.
The DX ENGINEERING SITE: has a type of pivot for
vertical antennas. One could be built as well with some
effort. MFJ has a hand adjustable coil with a clamp. This
is my idea of a Field deployable vertical that doesnt
need radials and can be set up quickly..ie FIELD DAY.
If all goes well..I will try to build this antenna for this
years FIELD DAY..2011 and I will write it up and try it out
over a few weeks.
To the left is pictured a fold over vertical antenna system that is offered by
a commercial outfit called DX ENGINEERING. I noticed on their site they
also sell light weight TOP HAT RADIALS and plenty of hardware for building
your own vertical antenna.
This system looks quite simple. OBLONG hole that allow you to move the
bottom bolts up and out and then tilt the antenna down for adjustment or
to work on the antenna or..(what I do)..lower it down in high winds and
larger storms for extra safety. The lower section of the vertical can also be
bought..or (what I do)..buy a used old 14avq or other vertical and use the
parts to make a new antenna.
|theres more to come. perhaps a second page in early JUNE as I resurrect this antenna and build it and use
it IN PREPARATION..FOR FIELD DAY..2011!!! If conditions seem good on 15 and 10..I might build a dual
band version for those bands...thats the plan anyways..73 earl ve3ab