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.

– – – – – – – – – 

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.

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 corner 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 Website 2M-(220-)440 & SCAN-III Vehicle Photos

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.]

Adjustable mounts that often work well for top or side of hatchback opening;
near top corner if appropriate is often best:
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  COMPACtenna Installation - Adjustable Mount - NMO Antenna Hole Mount with Cable - Diamond C213SNMO - Requires ONLY .375in. HOLE

Submitted by John. W0RS:
COMPACtenna 2M-220-440 Photo W0RS Mobile Installation Photo 2 with SWR's  COMPACtenna 2M-220-440 Photo W0RS Mobile Installation Photo 1

COMPACtenna Installation NMO Bracket Mount for Railing, Ladder

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
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.]
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.]

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

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.
Experimentation 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 below regarding use of radio built-in automatic internal tuners, often sufficiently effective.]

Parasitic effects of ‘nearby’ metal objects can occur with proximity relative to wavelength.
Some experimentation with location changes of the antenna
can be very helpful in improving resonance/SWR.
Pay attention to heating ducts, wiring, downspouts, etc.

Receive performance can be very negatively affected 
in noisy RF environments such as due to switching power supplies in the home.
    [See further comments regarding reception below.]

In addition, switching power supplies used to power a 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.

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.

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.]
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 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 a ‘floating capacitor’ effect over the ground plane counterpoise
and have deleterious effects on (V)SWR.

Many small HF antennas still require an expansive ground plane counterpoise, such as with multiple long wires,
making installation in ‘close’ 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.]
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; use at the radio end of the coaxial feed, add to the antenna end if  improvement occurs there.
When split ferrite beads are used along a coaxial cable, often 10 or more are needed.
[Tucking the magnet mount coaxial cable under the metal sheet counterpoise frequently improves SWR as well.]

This design is intended for the metal plate/e.g. table top to have coupling to earth for overall effective ground plane counterpoise results, and to reduce ‘common mode’ currents. 
Some coupling/counterpoise ‘extension’ result is desirable; not too much as can happen on a hot sticky expansive asphalt parking lot, but not too little. 
Often the ~3′ X 3′ plate set on ‘dry’ ground/the floor of a house/building structure is quite effective, as well as on a metal table top and first floor attic/closet.
However, when raised from the ground, a ‘Special Ground Plane Counterpoise’ can become quite helpful.
Also, because of variabilities in the installation environment with also potential coupling to nearby metal structures, the essential counterpoise becomes altered and the ‘Special Ground Plane Counterpoise’ discussed here can be quite helpful as well.
Furthermore, sometimes obtaining center-frequency-band resonance and good SWR is challenging due to much parasitic interaction of surrounding metal objects in general, i.e. regarding the center-fed element signal as well.
For example, at the 20 meter band substantial metal objects 15′ away are at about 1/4 wavelength separation!
Standard cooking type Aluminum foil 12-18″ wide is a good option.
Length of this counterpoise ‘leg’ may be about 8-15 feet for example; ~12′ is often quite effective.
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 configuration’
with the assembly ‘turned’ to a position with the one leg horizontal and the short COMPACtenna technology leg vertical.

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.]

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’ isn’t seen on the Signal Strength meter, nor is it 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.
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).