Hi
I have note from George and its on our webpage
https://www.pi4cc.nl/link/extra.php
Peter
PC2A
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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