16:1 Baluns/Ununs

Coax Jumper Choke - RG-8X - RFI Range: 1.8-65 MHz, -30 dB Noise Reduction, 1.5KW PEP, Magnetic Loop, Antenna Choke

SKU JC-1-1500-3
$29.95
Bulk pricing available for quantities of 2 units or more
1
Buy more, save more
QuantityPrice per itemDiscount
2 items$25.9513% off
Save this product for later
Customer reviews
No reviews yet. Only signed-in customers who bought this product can leave reviews. To leave a review, sign in
Share this product with your friends
Coax Jumper Choke - RG-8X - RFI Range: 1.8-65 MHz, -30 dB Noise Reduction, 1.5KW PEP, Magnetic Loop, Antenna Choke
Product Details
MPN: JC-1-1500
Country/Region of Manufacture: USA

Simple Jumper Feed Line Choke

The simplest, most cost effective feed line choke is a ferrite ring installed as shown in the picture (at the antenna feed point) to stop feed line radiation or at the radio end of the coax to suppress common mode coax noise current on the coax braid.

Improves antenna pattern by preventing your dipole from becoming a tripole

Suppresses pesky coax braid radiation and RFI

Reduces coax braid common mode current up to -30 dB ( 6 "S" units) on receive

Use one choke for each antenna feed line

Add a double female barrel connector to act as an "extension" of the existing coax.

Magnetic Loop Users: use 1 JC-1-1500 at the antenna feed point to keep all of transmit power on antenna and another at radio end to remove common mode noise received on the coax braid.

Need the ring only and not the jumper, select F240-31-1 as the part #.

Question: Assuming the JC-1-1500 uses mix 31, why is the effective range 1.8-65MHz instead of 1-300MHz?

Answer: Look at measurement chart to see the answer - it takes at least -12 dB of common mode rejection to see/hear a noticeable difference with and without choke. Yes the spec for mix 31 say it is good to 300 mhz but at that frequency the CMRR is very small and hasn't much of effect on common mode rejection. Also when you form a choke with coax your are actually creating a parallel tuned circuit at a certain resonant frequency determined by the coax capacitance of approximately 28 pf/foot and the inductance of the coil. The graph shown that the max CMRR is roughly -30 dB between 1-21 MHz and slightly less as you go higher in freq (the resonant freq of the JC-1-1500 is roughly 10 MHZ and broad banded by the use of the ferrite). Above 6 meters CMRR becomes low so as not to be very effective. If you want to use the choke on higher bands you need to change ferrite mix and the number of turns of the choke so the center resonant freq is higher.

Ferrite are in reality frequency dependent resistors and the specs say they have a resistive component above 1 mHz and under 300 mHz but the resistance (or CMRR) has to be high enough to be effective. We publish the effective range so you know what to expect when used.


16:1 Baluns are useful between 750-850 ohm balanced loads where the impedance at the  end of the feed line is 800 ohms (1/2 wavelength feed line), or high impedance feeds for rhombic,  T2FD and traveling wave antennas.

16:1 Ununs are useful between coax and long wires with a load impedance near 800 ohms like a beverage antenna.  Shortwave listener antennas also can benefit with the 16:1 unun and it may provide a better match than 9:1 ununs – this means quieter noise levels and stronger signals so you can hear distance stations easier.