Chameleon SS17 whip without coil - extended length by band?

[montyhouse]

I have a SS17 whip and a MFP ground rod spike that I'd like to use without a coil, mainly for 10m but up to 20m. (MFJ claims it can be used as such up through 20m.) My question is whether anyone has "tuned" this whip to low(est) SWR at varying bands without a coil. I checked it with my NanoVNA today, and the lowest I could get it (using 25' counterpoise) was around 2.1 near 10m calling freq (~28.400). I looked at Chameleon website and people are using it coil-less but no one posted antenna length by band. Thanks.

 

[prcguy]

The problem your having is you made an inverted V dipole on its side with just one counterpoise. Think of a dipole and your only adjusting the length of one leg of the dipole and now you are forcing the coax to the party and inviting it to be a radiating element. Install at least 3 ground radials and if they are on the ground you want a lot more and then you can adjust the SS17 to a 1/4 wavelength on 20, 17, 15, 12 and 10m and the VSWR should be low.

If you use the same whip with the Chameleon 5:1 transformer at the base you will need a tuner and if you use just one counterpoise wire it will tune to a very low VSWR, but you will have the same problem of a dipole with one untuned element and its laying on the ground incurring lots of bonus ground loss and efficiency will be degraded. If you want to run just one counterpoise wire get everything off the ground and treat it like the radiating hot element that it is. When you have two or more equal length radials going opposite directions radiation is canceled in those radials.

I have a SS17 whip and a MFP ground rod spike that I'd like to use without a coil, mainly for 10m but up to 20m. (MFJ claims it can be used as such up through 20m.) My question is whether anyone has "tuned" this whip to low(est) SWR at varying bands without a coil. I checked it with my NanoVNA today, and the lowest I could get it (using 25' counterpoise) was around 2.1 near 10m calling freq (~28.400). I looked at Chameleon website and people are using it coil-less but no one posted antenna length by band. Thanks.

 

[montyhouse]

Thanks to PRC's help, I made some good progress on using the SS17 whip for at least 10m (testing with NanoVNA). The first thing I did was take the MFJ 25' counterpoise and raise it (with the help of a hiking pole); SWR immediately went down from 2.05 (on ground) to 1.4 (raised). (I also tried no counterpoise after reading some internet speculation, e.g., "... a counterpoise isn't needed for 10m....," and SWR went up to 2.73.) Then, based upon this ARRL post, I tried an 8'2" (1/4 wavelength) 12 ga wire--raised and at a 90 deg angle to antenna coax--and was able to get it down as low as 1.12 (with ~3 3/4 sections of the SS17 extended--an overall antenna length of 8'5"). So, I'm off to the races. I'll pair up with my IC-705 and do fine tuning via my MAT ATU and the unit's integral SWR meter. Thanks for the hand.

 

[prcguy]

Just remember with a single counterpoise wire you have made a dipole and that counterpoise wire will radiate as much as the whip. If you add two or more equal length counterpoise wires (ground radials) they will not radiate and will not need to be tuned. I would use a lot of short ground radials like 8 or 10 wires just 10ft long each should be adequate for 20-10m.

Thanks to PRC's help, I made some good progress on using the SS17 whip for at least 10m (testing with NanoVNA). The first thing I did was take the MFJ 25' counterpoise and raise it (with the help of a hiking pole); SWR immediately went down from 2.05 (on ground) to 1.4 (raised). (I also tried no counterpoise after reading some internet speculation, e.g., "... a counterpoise isn't needed for 10m....," and SWR went up to 2.73.) Then, based upon this ARRL post, I tried an 8'2" (1/4 wavelength) 12 ga wire--raised and at a 90 deg angle to antenna coax--and was able to get it down as low as 1.12 (with ~3 3/4 sections of the SS17 extended--an overall antenna length of 8'5"). So, I'm off to the races. I'll pair up with my IC-705 and do fine tuning via my MAT ATU and the unit's integral SWR meter. Thanks for the hand.

 

[prcguy]

As a follow up, when I'm using my various portable HF verticals, I made 12 ground radials 20 ft long each and crimped them all into a single lug with 1/4" hole. That makes for quick deployment so you don't have to mess with a bunch of individual wires and it connects to a 1/4" bolt on my various mounts. I find a dozen 20ft ground radials are ok for 40m and up but if your only interested in 20m and up I think 10ft radials are fine. Just use a lot of them.

 

[montyhouse]

As a follow up, when I'm using my various portable HF verticals, I made 12 ground radials 20 ft long each and crimped them all into a single lug with 1/4" hole. That makes for quick deployment so you don't have to mess with a bunch of individual wires and it connects to a 1/4" bolt on my various mounts. I find a dozen 20ft ground radials are ok for 40m and up but if your only interested in 20m and up I think 10ft radials are fine. Just use a lot of them.

I cut three 8' 14 ga wires and connected to stake then elevated off the ground. The lowest SWR I could get via my NanoVNA was 1.19. This is around what I got with the single elevated wire (1.12). I then hooked up my IC-705 and checked SWR. (The NanoVNA can be a little tricky, e.g., waving around a fair bit....) All readings with this single counterpoise were <1.2. (I understand your dipole analogy in your initial reply, however.)

 

[prcguy]

VSWR is not everything. If you could do a field strength test 100yds away with one counterpoise wire vs three you would see an increase in performance. If you go from three ground radials to 12 you will see another increase. Going from 12 to 32, etc, very little increase.

I cut three 8' 14 ga wires and connected to stake then elevated off the ground. The lowest SWR I could get via my NanoVNA was 1.19. This is around what I got with the single elevated wire (1.12). I then hooked up my IC-705 and checked SWR. (The NanoVNA can be a little tricky, e.g., waving around a fair bit....) All readings with this single counterpoise were <1.2. (I understand your dipole analogy in your initial reply, however.)

 

[montyhouse]

VSWR is not everything. If you could do a field strength test 100yds away with one counterpoise wire vs three you would see an increase in performance. If you go from three ground radials to 12 you will see another increase. Going from 12 to 32, etc, very little increase.

Excellent point. Do you think it's as much of a factor with QRP?

 

[prcguy]

Its especially important for QRP, you have to make the most of your flea power.

Excellent point. Do you think it's as much of a factor with QRP?