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


Easy to Install        Easy to Use


COMPACtenna Science & Technology is designed for the Convenient use of UPPER Corners of Vehicle
[VHF/UHF 7.5″ & 9″ models and (stationary) 20″ models (20M/2M/440, CB/2M/440, and SW)].
COMPACtenna is LESS restrictive than most antennas which have only one optimum spot, being the center of the roof ONLY.
All COMPACtenna models have MULTIPLE optimum possible locations, the upper corners of the vehicle.
Some have found, depending on their vehicle construct and mount style they use,
that they also get good results from the corners of the hood, or trunk lid, etc.
But not always, so these locations are not officially among the recommended ‘corners’.
The COMPACtenna is designed very short, allowing most people
to use the UPPER corners of their vehicle.
YouTube – HamRadioConcepts on COMPACtenna model 2M-440 Performance & SWR
COMPACtenna YouTube HamRadioConcepts model 2M-440 Performance & SWR
With a short antenna, the hot voltage point is quite close to the ground plane counterpoise with consequently low resistance.
The high inductance and capacitance of the COMPACtenna magnetic field resonator design
are balanced at the corners for proper overall resistance in a short antenna,
working in conjunction with the downward/sloping metal of the
vehicle at the corner locations having increased resistance effect.
And this geometric dimensional counterpoise also results in 
a substantially omnidirectional VHF/UHF pattern.
HF azimuth coordinate pattern is also substantially omnidirectional
due to capacitive coupling of the vehicle to ground/water table, especially at frequencies < 20 MHz.


VHF/UHF 7.5″ & 9″ models with CompacCounterpoise – Ground Plane Counterpoise Radial Kit
20″ Models 20M/2M/440, CB/2M/440, and SW (Shortwave):  Small Ground Plane Counterpoise
by Capacitive Coupling (Metal Sheeting/Foil) to Earth
and Overall Tuning (SWR & Effective Counterpoise – Performance)


– – – – – – – – – 


Follow local building codes including NEC grounding/lightning/etc. and NFPA guidelines.
Follow applicable RF-Exposure Regulations.
Professional Installation is recommended.
Don’t touch any part of antenna structure, ground plane/counterpoise, mounting/support, feedline, grounding,
lightning arrestor components/systems nor any other part of installation and related parts/structures while transmitting.


– – – – – – – – – 


7.5″ & 9″ COMPACtenna models    Vehicle and Base Station Application

2M/220/440 (7.5″)    2M/440 (7.5″)    2M/440+(9″)    SCAN-III (9″)    LMR-I (9″)


Here are photos of the 7.5″/9″ models on NMO magnet mounts:
 COMPACtenna Photo 2M and SCAN-III antennas on Car AT CORNERS
Magnet mount on corner of pickup truck cab:

COMPACtenna Photo 7in Antenna Magnet Mount on Truck Cab

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″ 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.]
For VHF/UHF, ‘flatter style’ magnet mounts often provide best SWR’s, e.g.,
COMPACtenna Installation NMO Magnet Mount - LAIRD BLACK small Center PIN
YouTube – LCARA Demonstrating Excellent SWR with ‘Flat’ Style Mount near Upper Corner of Vehicle
COMPACtenna YouTube LCARA 'Flat' style Mount


Antenna Mount Types
Through-Hole mounts have been found to work optimally more consistently than many other types. This style of mount commonly provides good juxtaposition between center and shield lead connections to antenna and ground plane counterpoise, which is particularly important with VHF/UHF, and they don’t have the challenge of adequate capacitive coupling to ground plane counterpoise that some other style mounts can have, particularly at HF frequencies.
L-Bracket & Adjustable Bracket attached-to-vehicle-metal with screws type mounts are also favorites by many for similar reasons.
As can be seen by the formulas, etc. above, magnet mount capacitive coupling is often quite good at VHF/UHF and some HF frequencies.
Adjustable bracket mount with screws into vehicle body metal, upper corner hatchback style;
Thru-Hole Mount near corner of roof:
COMPACtenna Installation 7in, 9in Adjustable Hatch, Through-Hole Mounted Photos
ADJUSTABLE BRACKET MOUNTS – Sturdy, good ground:
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
Below:  A couple NMO through-hole mounts to consider for adjustable mounts


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


Standard L-brackets can be good too, such as on the upper back corners of the cab of pickup trucks, even aluminum ones such as the newer Ford F-150:
COMPACtenna Installation NMO L-Bracket on Corner Pickup Truck Cab
COMPACtenna Installation NMO L-Bracket Coax PL-259




7.5″ and 9″ Models  –  Base Station Application

On COMPACtenna  CompacCounterpoise  Ground Plane Radial Base Station Adapter Kit:
COMPACtenna CompacCounterpoise Photo with SCAN-III



– – – – – – – – – 


20″ COMPACtenna models    Vehicle and Base Station Application

20M/2M/440   CB/2M/440   SW
20″ COMPACtenna models are designed for

securely mounted appropriate outdoor installations

as well as appropriate indoor installations,

and even on a stationary vehicle
as in campgrounds, POTA.

They are not recommended for vehicles in motion.
COMPACtenna Installation OUTSIDE, Inside 20in Base Station models 20M, CB, SW 9.15.21
COMPACtenna Installation 20in Antenna in Attic Photo 9.15.21 WITH LABELING
See below: COMPACtenna Science & Technology – ANTENNA IS DESIRABLY PRE-TUNED


COMPACtenna 20in models 20M, CB, SW on vehicle photo 9.1.21

COMPACtenna HF 20&amp;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  7.5″ & 9″ COMPACtenna models  section above.
Other style mounts such as through-hole types may also be used.
COMPACtenna Installation Gum Drop-Beehive-Dome Style Antenna Mount   COMPACtenna Installation Heavy Duty Style Antenna Mounts
COMPACtenna Installation - Adjustable Mount - Firestick 'CB' models with NMO hole mount option discussed
COMPACtenna Installation Ball Mount CB style Upper Corner Pickup Truck Cab PHOTO


Antenna Mount Types
Through-Hole mounts have been found to work optimally more consistently than many other types. This style of mount commonly provides good juxtaposition between center and shield lead connections to antenna and ground plane counterpoise, which is particularly important with VHF/UHF, and they don’t have the challenge of adequate capacitive coupling to ground plane counterpoise that some other style mounts can have, particularly at HF frequencies.
L-Bracket & Adjustable attached-to-vehicle-metal with screws type mounts are also favorites by many for similar reasons.
As can be seen by the formulas, etc. on this page above, magnet mount capacitive coupling is often quite good at VHF/UHF and some HF frequencies.
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.



Optimizing Installation of small (HF …& VHF/UHF) 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.
Some experimentation/optimizing can prove quite beneficial for your particular system; see below.
One of the most common problems in any radio-antenna system is a connection problem.
A magnet mount may not have good continuity (internal disconnect); some are reported to be more reliable.
Connectors and adapters can be bad.
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.
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

With other ‘small’ antenna technologies it is ‘standard’ that one needs to tune the antenna structure itself,
either manually or remotely, sometimes changing the structural tuning for each frequency change.
With COMPACtenna Science & Technology, there is desirably no tuning of the antenna itself.
Instead, the ‘structural tuning’ is only when necessary and accomplished essentially by changing the position
of the antenna/antenna+counterpoise system, such as moving the antenna somewhat on the vehicle to an even better SWR-matched position 
generally near a top corner, moving a VHF/UHF antenna on CompacCounterpoise in an attic where there is interaction with nearby metal structures, 
and with 20″ HF-CB-SW models on metal sheet/foil as below.
This is typically needed only when substantial parasitic interaction is ‘near’/influencing the antenna/counterpoise structure. 
20″ HF-CB-SW models: 
With the (magnet) mount at a corner of the metal sheet, and the 8′ aluminum foil extension centered at the opposite side (see photos above),
often no/little adjustment is needed with an installation outside on the ground, away from the house/building
and substantial (relative to wavelength) metal structures.
When inside, especially on an elevated floor/attic location, coupling can occur (as is expected) to metal in the house.
This can ‘drive’ the resonant center-frequency downward, and can overall ‘detune’ SWR/performance somewhat.
With ‘standard tech.’ antennas tuning the antenna structure sometimes helps, sometimes not
because changing location and overall configuration of antenna and counterpoise is necessary to ameliorate the coupling effect.
But that is difficult with these antennas because the antenna and their counterpoise are both typically quite larger than the COMPACtenna antenna/system design.
Even ‘small’ standard tech. antennas are substantially larger than COMPACtenna typically.
And the extremely short loaded standard tech. antennas have very poor performance (and commonly still require a large ground plane).
Magnetic loops are small, but have several of their own challenges.
There are three things available with the COMPACtenna to mitigate this in different locations variably by:
Moving the magnet mount a few inches or to the other corner on the same side (sometimes switching to the side of the aluminum).
Shortening the aluminum foil/folding it back.
Moving the antenna+counterpoise to a different location; sometimes just a few feet away.
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.
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.]
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 ‘Transmitter Protection’ near 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.
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.
These can all 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!
Of benefit can be toroids/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 help 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.


Having the   ANTENNA OUTSIDE   often substantially reduces RF noise in that much of it commonly originates from within the house.
But simply creating a separation can be productive.
Distancing of the antenna from the computer and electronics for best reception is often a matter of experimentation.
Try different places at different distances.
(One ‘rule of thumb’ is 15 feet or more away.)
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/SW transceivers/receivers
and even for (especially non-FM such as SSB) VHF/UHF transceivers/receivers. 
RF ferrite beads/toroids on power leads at the power supply can be helpful.
RF from the antenna itself through the air with proximity to the radio/equipment
can cause similar problems.
Increasing distance from the antenna to the equipment can be very helpful, and decreases RF exposure.
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.
Quite helpful can be few loops of the coax as a choke at/near the antenna end of the coaxial lead,
a toroid core or Ferrite (split) beads at both the antenna end and the radio end of the coaxial lead.
Check results including SWR.
When (split) ferrite beads are used along a coaxial cable, often 5-10 or more are needed.
Garage Door Openers
Avoid proximity to automatic garage door openers;
activation can occur.
A good System Ground is important. 
Stray RF 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 in certain (elevated from earth) situations.]
such as   Power, Microphone, Speaker, Amplifier, Data, PC, and Accessory   Leads/Wires/Cables. 

Transmitter Protection:
Check SWR with an antenna analyzer if possible.
Modify your installation for improvement if needed.
Reduce power output as appropriate.
Use an external tuner if necessary:
    Occasionally indicated for 20″ models.
    Improvement is generally adequate for 7.5″ & 9″ models by mounting location/style change (see above).
COMPACtenna Installation SAFETY SHEET 8.24.21