Clifton Laboratories 7236 Clifton Road  Clifton VA 20124 tel: (703) 830 0368 fax: (703) 830 0711



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Z1501D Active Antenna

Revision History
Created 19 February 2010
23 February 2010. Small changes in pricing table to reflect UHF cable option and clarify options
04 March 2010. Updated the intermodulation paper to fix an error at page 17.
22 April 2010. Added VLF recording page link
25 December 2010. Added Z1203B material

Table of Contents



The Z1501D is an electric field responding �active� antenna, employing a high impedance field effect transistor input stage to efficiently couple electromagnetic field from a physically short antenna to a low impedance (50 ohms) load.

The Z1501D allows efficient reception of frequencies from 20 KHz to 30 MHz (usable beyond 100 MHz with reduced performance) with a single relatively short vertical rod antenna.

There are many active antennas available, ranging in price from inexpensive to several thousand dollars. The Z1501D's provides performance comparable to the best available antennas but at a far more affordable price, particularly if purchased as a kit.

Unlike some high performance active antennas, the Z1501D does not "pot" the circuits in epoxy, making repair impossible by the user. Clifton Laboratories uses a different approach. A detailed construction, operation and maintenance manual permits the owner to maintain and repair the Z1501D for many years of enjoyment.

The Z1501D is mostly a surface mount kit, but all the parts are "large" in the surface mount context, being 1206 size or larger.






Printed circuit board 2 inches x 3 inches (51 mm x 76 mm); when enclosed in  weatherproof enclosure  4.5 inches x 2.5 inches x 1 inch (114 mm x 63 mm x 25 mm) excluding mounting flange.

DC Ratings

Voltage not to exceed 15V, negative ground, positive to coaxial cable center conductor.  Typical current consumption 100 mA. Performance based on 13.8V delivered to active antenna.

Output impedance

Designed to drive 50 ohm coaxial cable; 75 ohm cable may also be used.

Frequency Range

20 KHz � 30 MHz; usable to 100 MHz with reduced performance.

Insertion Loss

When measured with 50 ohm termination on input, 2.5 dB typical over range 10 KHz � 30 MHz; not to exceed 3.5 dB, measured with Clifton Laboratories Z1203A power coupler.

3rd Order Intermodulation Intercept

With test tones of 3.007 and 4.011 MHz, adjusted for 0 dBm output from the Z1501D, and a 15 pF/50R whip simulation adapter at the input connector: *

3rd order output intercept (OIP3): +40 dBm.

2nd Order Intermodulation Intercept

With test tones of 3.007 and 4.011 MHz, adjusted for 0 dBm output from the Z1501D, and a 15 pF/50R whip simulation adapter at the input connector: *

Worst case 2nd order output intercept (OIP2): +73 dBm at 7018 KHz, best case > +85 dBm at 1004 KHz.

Maximum Safe Input Voltage

> 1 volt RMS at Z1501D input terminal. The Z1501D has been tested with 1 watt transmitted power applied at the input, without damage. However, caution should be used if the Z1501D is to be installed close to transmitting antennas.

Antenna Rod Length

Recommended length 60 (1.5m) inches minimum to 120 inches (3m) maximum; shorter and longer lengths may be used depending upon the local RF environment.

* Click the title to download a detailed analysis of the test protocol and measured results for 2nd and 3rd order intermodulation performance, titled �Observations on 2nd and 3rd Order Intercepts of the Clifton Laboratories Z1501D Active Antenna.�



Item Price Comment
Z1501D Active Antenna kit $169.95 Kit includes printed circuit board and all electronic components, weatherproof enclosure with coaxial pigtail, mounting bracket, mounting clamps, antenna mount and a telescoping antenna. Input stage is pre-assembled and adjusted for best 2nd order intermodulation performance.
Z1501D and Z1203A Coupler kit $209.95 Package price for Z1501D active antenna kit and Z1203A DC power coupler kit
Z1501D and Z1203B Coupler Kit $229.95 Package price for Z1501D active antenna kit and Z1203B DC power coupler kit.
Z1501D Active Antenna assembled $229.95 Assembled and adjusted Z1501D active antenna, in weatherproof enclosure, with mounting bracket, coaxial pigtail, antenna mount and  telescoping antenna.
Z1501D Active Antenna and Z1203A Coupler assembled $289.95 Z1501D assembled as above and Z1203A DC coupler assembled.
Z1501D Active Antenna and Z1203A Coupler assembled $309.95 Z1501D assembled as above and Z1203B power couple assembled.
Second whip $16.00 If purchased with Z1501D. The Z1501D comes with your choice of a chrome plated medium length telescoping whip (5 ft / 1.5 meters) or a black finished long telescoping whip (approx. 10 feet / 3 meters). Some customers have expressed interest in a smaller second whip for portable use.

Both whips are sourced from BuddiPole and are high quality telescoping antennas.

Output Connector Type No extra charge BNC (female), UHF (SO-239 style) or CATV style "F" (female). Other connectors types are possible with special order.
Special connectors Contact Clifton Laboratories If a connector other than the BNC, UHF or F is required, contact Clifton Laboratories for availability and price.
Performance Documentation $20.00 This option means the Z1501D is supplied with measured 2nd and 3rd order intermodulation performance data, along with frequency response sweep. This option applies to assembled Z1501D units. It also applies to Z1501D kits if the purchaser returns the completed kit to Clifton Laboratories for performance documentation. In this case, an additional $7.50 for Priority Mail return to the purchaser (domestic US) applies.
2nd Order Intermodulation Adjustment for kits $7.50 postage (domestic US only) Although the input stage of Z1501D kits is supplied assembled and adjusted, Clifton Laboratories will adjust without a service charge assembled kits for optimum 2nd order intermodulation performance. A fee of $7.50 for priority mail return of the Z1501D printed circuit board applies. No performance data will be supplied with this service unless separately purchased.
Virginia Sales Tax 5% For orders shipped to an address within the Commonwealth of Virginia.
Shipping TBD Until experience permits a flat rate shipping charge for domestic US orders, please contact Clifton Laboratories for shipping charges. Normally domestic shipping will be via Priority Mail.

What do you need besides the Z1501D

The Z1501D construction and operation manual discusses installation in detail. In short, you will need the following:

  • A suitable support mast. This may be between 1" (25mm) and 2" (50mm) diameter and should be around 8 (2.5 meters) to 10 (3 meters) feet long when ground mounted.
  • Coaxial cable between the Z1501D and the DC power coupler. This may be RG-58 type 50 ohm cable or 75 ohm CATV cable. The Z1501D will work with either. If using CATV cable, you may wish to select the Type F connector option when ordering your Z1501D.
  • A common mode choke may be necessary or desirable to reduce noise pickup.
  • A DC power coupler, such as a Z1203A or Z1203B.
  • A suitable source of DC power, 13.8V at 130 mA typically is required when using a Z1203A coupler and Z1501D. The Z1203B does not require an external DC power supply.
  • Miscellaneous coaxial cable and connectors to connect the DC power coupler to your receiver.

A and B Coupler Differences

Either a Z1203A or Z1203B coupler may be used with the Z1501D Active Antenna. The differences between the "A" and "B" coupler are:

Property Z1203A Z1203B
Power Source Requires 13.8V DC from an external power source Powered from 120V/60HzAC mains. Includes external "wall wart" transformer. Z1203B has rectifier, filter and voltage regulator.
Output Voltage Depends on supply; normal range is 10-15V and operation above 16V is not recommended. Adjustable from 9V to 24V
Maximum Current Output 200mA 400mA
Active Antenna Connector BNC or Optional "F" BNC Only

If your radio room has a low noise analog 13.8V DC supply, the Z1203A is suitable. If you do not have 13.8V DC available, or if you prefer the advantages of an integrated power coupler, the Z1203B is suitable.


VLF Reception Sample

I've added a page with a recording of how the spectrum from 17 KHz to 100 KHz sounds at Clifton, VA with the Z1501D antenna. Not all installations will be as successful, of course, at suppressing 60/120 Hz "crud" and computer birdies, but I'm pleased with how well I've done. Click the following link for the page: VLF Signals with Improved Setup


Orders, Payment and Delivery

Z1501Ds are built as orders arrive. Please allow up to one week between order receipt and shipping. Your order will be acknowledged when received and tracking information provided when the product ships.

Payment may be made via PayPal to Or, check or money order to Clifton Laboratories at the address at the top of this page.

Until a flat rate domestic shipping charge is established, please contact Clifton Laboratories for a total price. When contacting Clifton Laboratories, please provide the following information:

  1. Kit or assembled?
  2. Z1203A or Z1203B to be included?
  3. Connector type�BNC female, F female or special
  4. Whip length to be supplied with the Z1501D, medium length or long.
  5. Second whip? If yes, which length.
  6. Do you want performance documentation?
  7. Shipping address

Z1501D in enclosure.

Z1501D installed on mounting bracket, with BNC female pigtail and antenna mount.


Z1501D installed on short mast with medium length whip


Z1501D  in Winter Testing with Long Whip