Topband: Battle Creek Special - 160 Resonance

Peter pc2a at
Sun Oct 30 01:50:41 EDT 2016


I have note from George and its on our webpage


Dear OM Peter:

Something you need to know about your website:

The Battle Creek Special is designed for use from 7.0 to 7.3 MHz and the
trap should be resonated close to 7.0, not 7.1 MHz.

On 80 meters the design frequency is 3525 KHz, and the bandwidth is 3500
to 3570 KHz. The trap needs to resonate at or below 3525. The trap
data you give will resonate at 3750 KHZ which will reduce the
performance on 80 CW and may give other problems. The capacitance to
resonante 9 uHy at 3.5 MHz is about 225 pfd.
The Battle Creek Special uses two pieces of RG-213 about 4 feet long, in
parallel, to get this capacity and they hang below the trap inside the
top section.
Please correct your diagrams to reflect this.

Also do not forget the 2:1 UnUn (9:4 UnUn also works) to bring the
impedance on 160 up to about 50 ohms.

With L=9 uHy, C is best at 229 or 230 pfd for resonance nearest 3500 KHz

With C = 200 pfd, L is best at 10.33 uHy for resonance at 3500 KHz

73 George K8GG Battle Creek, Michigan

Op 30-10-2016 om 0:16 schreef thoyer:
> I built this antenna several years ago. I never really had a good resonance
> on 160 though. Best I could do was 3.5:1 or so. I used the xcvr ant tuner to
> match it without issue.
> Since it had been up for many years I brought it down a couple weeks back
> for maintenance. I reworked the traps and adjusted the length of the first
> section to give me a better match in the CW portion of 40m.
> The reworked traps dip at approx 7.12mhz for the 40m trap and 3.5mhz for the
> 80m trap.
> Put the antenna back up today and have a nice match in the CW portion of 40,
> but the 80m resonance has shifted down to around 3.3mhz and I see no
> resonance on 160m.
> Some numbers from the MFJ analyzer:
> 40m 7.05mhz 44, 10 and 1.2 VSWR
> 80m 3.51mhz 91, 136 and 5.8 VSWR
> 160m 1.81mhz 18, 37 and 4.1 VSWR
> I have about 40 radials varying in length from 50 to 60 feet depending on
> the yard.
> The 80m loading wire is approx 15' long
> The 160m "L" is approx 72 feet long
> The overall height of the antenna is 50ft.
> Any suggestions for how to obtain a better resonance on 160?
> Tom
> W3TA
> _________________
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