COMPACtenna   …   COMPACT antenna
SMALL antennas       NO tuning (of antenna structure)       SMALL ground plane       HIGH Performance


COMPACtenna requires a ground plane/counterpoise as other antennas, BUT LESS.
Allowing greater flexibility in installations/locations.


– – – – – – – – – 


Follow local building codes including NEC grounding/lightning/etc. and NFPA guidelines.
See SAR and Transmitter Protection below.
Professional Installation is recommended.


– – – – – – – – – 


7″ & 9″ COMPACtenna models

2M/220/440 (7″)    2M/440 (7″)    SCAN-III (9″)


With many antennas, the single center-of-roof placement (with no sunroof) is strongly encouraged.
All the corners of a vehicle roof/trunk lid are unfavorable
for these ‘standard technology’ antennas.
Not true with COMPACtenna Science & Technology.
Those many locations are actually very desirable for the COMPACtenna,
providing many appreciated options.  
The COMPACtenna effectively utilizes the side-metal of the vehicle
(quarter panels, fenders, pillars, doors) as a vertical/sloping counterpoise
allowing greater flexibility in varieties of placements and ease of installation.
For best SWR and performance, mount your COMPACtenna at/near a corner of your vehicle.


The center-of-roof location can cause reduced resistance and increased (V)SWR especially at
VHF frequencies with short antennas due to the antenna high voltage point
being so close to extensive ground plane/counterpoise all around it.
But with substantial downward-projecting metal the resistance
beneficially increases with counterpoise signal enhancement
effect such that the numerous corners of roof/trunk
locations become excellent potential
installation site choices.
[See ‘Transmitter Protection’ at bottom of page.]


[As a receiving antenna, model SCAN-III performs excellently at any position on metal roof/trunk lid/fender.]


Here are photos of the 7″/9″ models on NMO magnet mounts:
COMPACtenna Photo 7inch Single Antenna on Magnet Mount on Vehicle  COMPACtenna Photo 2M and SCAN-III antennas on Car AT CORNERS
Magnet Mounts
Capacitive Coupling Reactance
A magnet mount provides good coupling,
particularly at VHF/UHF, with little capacitive impedance,
and even with transmitting at HF down to ~7MHz (40 meters):
[20″ & 46″ models are not recommended for vehicles in motion.]
COMPACtenna Installation - Formulas for Magnet Mount Capacitive Coupling PAGE 1 of 2
COMPACtenna Installation - Formulas for Magnet Mount Capacitive Coupling PAGE 2 of 2
[Note that a magnet mount with a “thick” rubber bottom ‘boot’ will decrease capacitive coupling.]


COMPACtenna Installation 2M-220-440 Mount Types

[For rail/bar mounting, positions at/near the end of a horizontal rail/bar generally result in better SWR’s.]


Roof Racks/Rails:
Roof racks can work well.
Some are grounded, some are not.
With COMPACtenna technology either can work.
It’s nice when the rack rail is exposed metal as opposed to plastic coated,
but even then the clamp often provides enough capacitive coupling to the rail as a ground plane counterpoise.
A rail can serve as an effective counterpoise for this antenna technology,
 particularly when mounted near the end of a horizontal rail,
especially when that end is near a corner of the vehicle.


ADJUSTABLE MOUNTS – Sturdy, good ground:
COMPACtenna Installation - Adjustable Mount - Universal Radio Info. - WORKMAN mount  COMPACtenna Installation - Adjustable Mount - Universal Radio WORKMAN Hatchback Install PHOTO


COMPACtenna Installation - Adjustable Mount - Firestick 'CB' models with NMO hole mount option discussed
Above:  Firestik SS204 Door/Hatch Jamb Mount on Left; SS274 Hood/Trunk Channel Mount on Right


COMPACtenna Installation - HUSTLER CHMA-P .375 in hole NMO mount for .5 in hole of Adjustable Mount
Hustler CHMA-P at Ham Radio Outlet


Many vehicles allow passage of small ~0.2″ diameter RG-58 coaxial cable as with the Hustler CHMA-P mount above,
but some vehicles have especially narrow gaps between the closed hatch/door.
The Diamond NMO mount below has 1/8″ diameter coaxial cable:
COMPACtenna Installation - Adjustable Mount - NMO Antenna Hole Mount with Cable - Diamond C213SNMO - Requires ONLY .375in. HOLE
Diamond C213SNMO Mount at DX Engineering
Diamond C213SNMO Mount at Ham Radio Outlet


Submitted by John. W0RS (see Diamond K400/K412 Series Mounts):
COMPACtenna 2M-220-440 Photo W0RS Mobile Installation Photo 2 with SWR's  COMPACtenna 2M-220-440 Photo W0RS Mobile Installation Photo 1


Motor Home/RV, Boat
Consideration for railing of Motor Home/RV or Boat (see comments on rail mounting above):
[For marine use another option is using a Base Station Adapter Kit (see below) in a Base Station style configuration.]
COMPACtenna Installation Bracket Mount w 5-8in hole for 3-8in NMO COMPACtenna Installation RV Roof Rack Photo  COMPACtenna Installation Boat Railing Antennas PHOTO
MOTOR HOME   antenna      (
COMPACtenna REVIEW 2M,220,440 on MOTOR HOME INSTAL Gary, KF4GGK - Gerhard Spangenberg


Tim Bauer’s Truck Stake Pocket Bracket for NMO Mount (Athens, AL):

COMPACtenna Installation - Tim Baurer's Stake Pocket Bracket for NMO Mount (Athens, AL)

Magnet mount on corner of truck cab:

COMPACtenna Photo 7in Antenna Magnet Mount on Truck Cab

Other truck mounts including for aluminum cabs where a magnet mount will not work:
Ford F-150  3rd Brake Light High Mounts:


Similar Mounts for Chevrolet, Ford, Ram


L-Bracket, Fender/Bracket mounts for Trunk, Hood Groove, etc.
COMPACtenna Photo Bracket-Fender Mount - NMO     COMPACtenna Photo NMO mount L-Bracket
compactenna on 4x4 photo




Base Station Application

[Follow local building codes including NEC grounding/lightning/etc. and NFPA guidelines.]
[See SAR below.]
[See comments regarding reception and RF noise, including due to Wi-Fi Routers, 
in section below on ‘Optimizing Installation of small (HF) antennas in ‘small spaces’.]
Base Station Antenna ground radials kits work very well with the VHF/UHF COMPACtennas
with the ground plane counterpoise elements bent downward to 70 degrees below the horizon.
COMPACtenna Installation 7 inch models on BSAKIT

COMPACtenna Installation 7in File Cabinet, Steel Table

7″ & 9″ models Available at:

COMPACtenna model 2M/220/440 at Universal Radio
COMPACtenna model 2M/220/440 at Ham Radio Outlet
COMPACtenna model 2M/220/440 at DX Engineering
COMPACtenna model 2M/220/440 at KB Cubed Hamfests
Heartland Radio   —   eBay affiliate


COMPACtenna model 2M/440 at Universal Radio
COMPACtenna model 2M/440 at Ham Radio Outlet
COMPACtenna model 2M/440 at DX Engineering
Heartland Radio   —   eBay affiliate


COMPACtenna model SCAN-III at Universal Radio
COMPACtenna model SCAN-III at Ham Radio Outlet
COMPACtenna model SCAN-III at DX Engineering
Heartland Radio   —   eBay affiliate


– – – – – – – – – 


20″  &  46″  COMPACtenna models

20M/2M/440   10M/2M/440   6M/2M/440   CB/2M/440   SW      HamR-7 Series
[Follow local building codes including NEC grounding/lightning/etc. and NFPA guidelines.]
[See SAR below.]
20″ and 46″ COMPACtenna models are designed for desired indoor placement. 
They may also be used outdoors mounted securely on a metal sheet/table/surface
and even on a stationary vehicle as in campgrounds, POTA.
They are not recommended for vehicles in motion.

Small Ground Plane/Counterpoise

Most antennas require large ground planes
with lengthy ground/counterpoise radials all-around the antenna.
The 20″ & 46″ COMPACtennas require only a small, minimum 3′ x 3′ metal sheet/mesh/grating below it.
[Smaller overlapping sheets may be used.]


46″ Models:

HamR-7    HamR-7Digi    HamR-7WARC

20″ Models:







COMPACtenna 20M-2M-440 on floor in house  COMPACtenna 20in ATTIC PHOTO - CROPPED       COMPACtenna Installation - Enclosed Patio - 20 in. antenna on Patio Table  COMPACtenna HamR-7 Photo Resized and Trimmed

COMPACtenna HF 20&46in Antennas 3.8in-24 mount, PL-259 PHOTO

A good quality magnet mount, such as the Hustler MBM is recommended.
COMPACtenna Installation Hustler MBM Magnet Mount
Magnet mount installation is shown here.
See Magnet Mount – Capacitive Coupling Reactance (calculations)
in  7″ &9″ COMPACtenna models  section above.
Other style mounts such as through-hole types may also be used.
COMPACtenna Installation Patio 20in&46in Antennas Heavy Duty Mount
COMPACtenna Installation Gum Drop-Beehive-Dome Style Antenna Mount   COMPACtenna Installation Heavy Duty Style Antenna Mounts
See “Adjustable” Vehicle Mounts in 7″ & 9″ section above.
[20″ & 46″ models are not recommended for vehicles in motion.]


Optimizing Installation of small (HF) antennas in ‘small spaces’

Here are some techniques that can help achieve the successes so many have.
Each situation is different.
Often the installation-to-operation is rather straightforward.
When there is substantial surrounding (metal) interaction in a particular installation,
some experimentation/optimizing can prove quite beneficial for your particular system.


Each antenna is hand-tuned for the SWR to ‘dip’ in each specified band,
but especially due to variabilities in installations and surrounding environments,
a good External Antenna Tuner may be desired
to realize this antenna’s full broad performance capabilities.
[See comments in sections below regarding use of radio built-in automatic internal tuners, often sufficiently effective.]
With other ‘small’ antenna technologies it is standard that one needs to tune the antenna structure itself,
either manually or remotely, changing the structural tuning for each frequency change.
With COMPACtenna Science & Technology, there is desirably no tuning of the antenna itself.
Instead, the ‘tuning’ is only when necessary and accomplished essentially by changing the position
of the antenna system (and possibly counterpoise structure – see ‘special ground plane counterpoise’ below).
This is typically needed only when substantial parasitic interaction is ‘near’/influencing the antenna/counterpoise structure. 
Once the proper position/configuration is in place, the antenna system is typically ready to operate
on many frequencies per band, expanded with the use of a radio internal tuner,
and even greater with an external tuner if desired.
Parasitic effects of ‘nearby’ metal objects can occur with proximity relative to wavelength.
Some experimentation with location changes of the antenna & metal counterpoise
can be very helpful in improving resonance/SWR; sometimes shifting
the magnet mount position even just a few inches on the metal 
can shift center frequency ‘dip’ and improve SWR results.
Pay attention to heating ducts, wiring, downspouts, etc.
[Avoid proximity to automatic garage door openers;
activation can occur such as with 6 meter band operation.]


Receive performance can be very negatively affected in noisy RF environments
due to unintentional radiators
such as switching power supplies, computers,
radio receivers which often use an intermediate frequency
which is detectable outside the radio, motors, dimmers, and corona from electrical powerlines,
and intentional radiators
such as wireless garage door openers, wireless microphones, RF universal remote control devices,
cordless telephones, wireless alarm systems, Wi-Fi transmitters, and Bluetooth radio devices.
Wi-Fi Routers are a common substantial problem, and often rather easily corrected!
[See further comments regarding reception (‘RECEIVE’) below.]


In addition, switching power supplies used to power the HAM Radio
can be very detrimental to BOTH TRANSMIT AND RECEIVE. 
The RF ‘noise’ from these switching power supplies can understandably affect receive, 
but also create oscillations that affect things such as transmit audio,
and even SWR measurement and tuner circuits!
Some have better filtering, but many operators recommend
non-switching transformer types especially for HF transceivers
and even for non-FM such as SSB VHF/UHF transceivers. 


RF from the antenna itself through the air with proximity to the radio/equipment
can cause at times improper function of SWR measurements,
(internal) matching systems and the radio itself
with such as transmit audio distortion as well as (other) feedback/oscillation issues.
Increasing distance from the antenna to the equipment can be very helpful.


A good System Ground is important. 
Stray RF from equipment can be substantially reduced.
Along with using the same power circuit/outlet as appropriate for your station equipment,
ground loop problems such as noise in reception can be dramatically reduced by a good common ground.
A poor RF ground can result in weak signals due to ground wire losses or radiation pattern distortion.
RF feedback can cause such things as modulation distortion or even stop your radio from working.
[An artificial Ground Unit can be helpful.]


Another consideration is that with any small HF antenna the concentrated RF electromagnetic field is close to the coaxial cable
lead and can get onto the outside of the shield of the coax which can give a path back to the radio/equipment resulting in similar
problems. Also the desirable level of capacitive coupling of the metal counterpoise to earth varies with installations, as does
parasitic coupling to surrounding structures, and common mode currents can occur. A few loops of the coax as a choke, a toroid
core, Ferrite (split) beads can help substantially; apply at the radio end of the coaxial feed and check results including SWR, add
to the antenna end if  improvement occurs there.
When split ferrite beads are used along a coaxial cable, often 5-10 or more are needed.
[Tucking the magnet mount coaxial cable under the metal sheet counterpoise frequently improves SWR as well.]


An additional matter is that of the radio equipment itself.
Just as radios vary substantially in their receiver selectivity specifications,
some radios and equipment are significantly more ‘immune’ to adverse RF
and even power lead noise effects which are not uncommon in small spaces.


One of the most common problems in any radio-antenna system is a connection problem.
Specifically here, the magnet mount may not have good continuity (internal disconnect); some are reported to be more reliable.
Some PL-259’s do not mate well with SO-239’s including at the transmitter, receiver, amplifier, test equipment.                           
Check your system as needed.
Tri- and quad- magnet mounts can produce added reactance and have deleterious effects on (V)SWR.
And some have lesser continuity from the plate to the magnets based on couplers/grommets
allowing independent tilt for roof, etc. contour.
Also, some may suffer from the continuity problem in the ‘Hub’ as described above.
Check your SWR.


Many small HF antennas still require an expansive ground plane counterpoise, such as with multiple long wires,
making installation in ‘small’ spaces a challenge.
The ‘tiny’ COMPACtenna HF antenna uniquely requires only a small ground plane counterpoise.
The commonly available one piece 3’ x 4’ galvanized sheet in home improvement stores is excellent.
Even easier to get through such as attic openings are two 2’ x 3’ galvanized sheets,
then overlapped a bit to make an excellent 3’ x 3’ platform for a 5” magnet mount in the center.
[Be careful with sharp edges/corners; consider duct tape on the edges & corners.]
In fact excess counterpoise dimensions can have an adverse effect on SWR.
One reason is that the ‘hot’ voltage point of the electric field of the short antenna
close to an expansive ground plane in multiple directions results in markedly decreased resistance.
[One person had poor SWR due to the galvanized metal sheet being on hot asphalt
creating a very large ground plane counterpoise coupling effect and therefore resistance decreased markedly.
Once he placed the magnet mount instead on a metal patio table all was well.]


This design is intended for the metal plate/e.g. metal table top to have coupling to earth for overall effective ground plane
counterpoise results, and to reduce ‘common mode’ currents. 
Often the ~3′ X 3′ plate set on ‘dry’ ground/the floor of a house/building structure, a metal table top and first floor attic/closet
placement are quite effective.
However, when raised from the ground, a ‘Special Ground Plane Counterpoise’ can become quite helpful.
This modification can also provide improvements where there is added counterpoise coupling to nearby metal structures with
variabilities in installation environments, and where obtaining center-frequency-band resonance and good SWR can be
challenging due to significant parasitic interaction with surrounding metal objects regarding the center-fed
antenna element signal.
For example, at the 20 meter band substantial metal objects 15′ away are at about 1/4 wavelength separation!
When applying this technique, use a few loops of the coax as a choke, a toroid core, or Ferrite (split) beads
at the (magnet) mount end of the coaxial cable.
When split ferrite beads are used along a coaxial cable, often 5-10 or more are needed.
Standard cooking type Aluminum foil 12-18″ wide is a good option; tucking an end under the ~3’X3′ steel sheet,
or between the sheet and the magnet mount can function well.
Length of this counterpoise ‘leg’ may be about 8-15 feet for example.
Watching SWR results while making length adjustments can help optimize your situation.
Think of this as essentially a ‘Complex-loaded shortened leg inverted-V style off-center fed configuration’
with the assembly ‘turned’ to a position with the one leg horizontal and the short COMPACtenna technology leg vertical.
Also, as mentioned above, sometimes shifting the magnet mount position even just a few inches on the metal 
can shift center frequency ‘dip’ and improve SWR results.


Internal tuners are often limited, where the before-tuning SWR must be below 3:1 (External tuners generally have broader
capabilities, often being able to tune much greater ranges of impedances.)  Internal tuners often work best by picking a (center)
frequency in the vicinity you desire to operate with an SWR (before auto-tune) below 3:1, then for example selecting a step
frequency width and the number of frequency points (‘bars’), and then use the auto-tune function.  This generally results in a
fairly wide frequency range with substantially good SWR’s.  [The built-in SWR measurement function with some radios produce
accurate results only when power output is at 5-10 watts, reduced to 5-10% on a 100 watt transmitter.  This adjustment during
tuning also helps protect the transmitter.  Operate the radio at higher output power per its specifications, often stated where
the SWR is <2:1 or <=~1.5:1; tube radios often <3:1.]
[See ‘Transmitter Protection’ at bottom of page.]


See the above and:
Regarding reception including with Shortwave model SW, every situation is different.
But there are some general guidelines, ‘rules of thumb’ and considerations that can be helpful.
Homes frequently have many switching power supplies such as for computers, printers, charging cell phones
and even LED lights.
These along with the computer and other electronic equipment themselves can generate RF noise.
Especially in radios-receivers with lesser filtering/shielding.
Front end overload and intermodulation problems can occur.
Sometimes the RF ‘noise’ is seen on the radio’s signal strength meter, yet sometimes it isn’t seen nor heard!
But it may be there nonetheless, causing desensitization of the receiver with poor reception of desired stations!
Grounding the shield of the coaxial antenna lead near the receiver helps so RF noise that gets onto the outside of the shield
tends to ground rather than into the radio.
Using a toroid/RF ferrite beads on the coaxial cable lead near the radio can be efficacious.
Also beneficial can be a toroid/RF beads on wires, cables and power leads at computers and electronic equipment and switching
power supplies and lamps because they can act as transmitting antennas.
A toroid/RF ferrite beads on a power strip cord helps reduce RF from connected switching power supplies getting to electrical
wires of your house that can act as substantial antennas.


Not only the switching power supply of the Wi-Fi router can cause RF noise, but
IS VERY EFFECTIVE; adding ferrite beads to the ethernet cable at the router can provide some additional noise reduction.
It is not uncommon to see a substantial noise level on the radio’s signal meter, both VHF/UHF and HF at various frequencies,
and for S-meter reading to drop to zero by simply applying the ferrite beads as above.


Distancing of the antenna from the computer and electronics for best reception is often a matter of experimentation.
Certainly getting receiving antennas outside of the house can be helpful, but also simply creating a separation
can be very productive.
Try different places at different distances.
(One ‘rule of thumb’ is 15 feet or more away.)


Limiting the number of connections is a good policy:

COMPACtenna HF 20&amp;46in Antennas Coaxial Jumper with SO-239 at one end Photo



COMPACtenna HF 20&amp;46in Antennas Coaxial Jumper with SO-239 Barrel Adapter Photo

Example SAR Calculator
   Example calculation:  
COMPACtenna SAR Calculation Example 7.4.20

20″/46″ models Available at:

6M/2M/440 at Universal Radio
6M/2M/440 at Ham Radio Outlet
6M/2M/440 at DX Engineering


10M/2M/440 at Universal Radio
10M/2M/440 at Ham Radio Outlet
10M/2M/440 at DX Engineering


20M/2M/440 at Universal Radio
20M/2M/440 at Ham Radio Outlet
20M/2M/440 at DX Engineering


ShortWave Radio at Universal Radio
ShortWave Radio at Ham Radio Outlet
ShortWave Radio at DX Engineering
Heartland Radio   —   eBay affiliate


CB/2M/440 at Universal Radio
CB/2M/440 at Ham Radio Outlet
CB/2M/440 at DX Engineering
Heartland Radio   —   eBay affiliate


HamR-7 — at Universal Radio
HamR-7 — at Ham Radio Outlet
HamR-7 — at DX Engineering


HamR-7Digi — at Ham Radio Outlet
HamR-7Digi — at DX Engineering


HamR-7WARC — at Ham Radio Outlet
HamR-7WARC — at DX Engineering

– – – – – – – – – 

Transmitter Protection:
Check SWR.
Depending on the result, reduce power output accordingly.
Modify your installation for improvement.
Use an external tuner as indicated:
    Not uncommon for 20″ & 46″ models. 
    Improvement is generally adequate for 7″ & 9″ models by mounting location/style change (see above).