Model CB-9-5000 is a 9:1 multi-core, balanced output balun housed in a NEMA enclosure box (4″ x 4″ x 2″) with top studs (TS) used to translate a 50 ohm input up to 450 ohms at RF power levels up to 5000 watts PEP when used with a matched load. With matched 450 ohm load the SWR over the frequency range 1 to 31 MHz is less than 2:1 on the coax feed side.
All power rating are PEP, 100%, continuous digital modes are 30% duty factor rating of PEP, FT-8 digital mode rated at 1500 watts.
Application note: If using 450 ohm ladder line on the output of the balun top studs, make sure the impedance seen at the balun end of the ladder line is near 450 ohms since the ladder line acts as an impedance transformer, the impedance at the end of the ladder line may be different than the characteristic 450 ohms of the ladder line. For example a 1/4 wavelength of ladder line will transform a high impedance at the antenna feed point to a very low impedance at the other end connected to the balun thus placing a very low impedance load on a balun expecting 450 ohms and such a load may damage the balun. The impedance seen at the balun output should be near 450 ohms for full power rating.
Testimonial
Hi Bob,
Radio: Flex-6700 running barefoot -10 to 100 Watts max.
Antenna: MFJ-1216 – 160/80 meter OCFD wire antenna with matching network.
Elevation: Over 60 feet AGL – fully extended.
Installed: Mid November 2013
I operate mainly on the digital modes running less than 50 Watts. All of the sudden after a few days operating with this antenna, I start to have RFI and my radio was acting up; such as changing bands, SWR changing values, radio failures and turning off. However, when I used my Hy-Gain 18 HT vertical on the same band none of the abnormality occurred.
I contacted MFJ and confirm that what I was noticing was a failure of their “matching network” AKA balun. They offered no solutions. Then I contacted Palomar Engineers and bought the 1:1 new toroid RF beads. I called Palomar Engineers and I happened to talked to you directly; regarding the on going issue with the MFJ antenna. I found out that the 1:1 balun was not what I needed (I was miss-informed by MFJ that it was 1:1 matching network.)
You offered to make the required balun 4:1 and the rest is history.
Here are my findings:
- No more RFI displayed on the monitors.
- Radio not acting up or turning off.
- The SWR at 160/80 meter is 1.2:1
- No antenna tuner required. (radio goes to Bypass automatically.)
- Worst SWR is on 10 meter with a 2:1 but still usable, with antenna tuner 1.5.
- One happy OCFD user!
Thanks to Palomar Engineers design and engineering for solving this issue.
73, Ernest – W4EG