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Author Topic: ZS6BKW vs ZS6BKW jr  (Read 4997 times)
WB4SPT
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« on: December 09, 2012, 01:36:43 PM »

I've seen a nice file comparing the full size ZS6BKW against the G5RV.  Has anyone done a similar study on the ZS6 vs the Jr?   I'm wiling to give up 75m on this dipole, wondering if 40 or 20 is hurt; and hoping for better 15m against all the full size variants.
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W5DXP
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« Reply #1 on: December 10, 2012, 05:30:23 AM »

I'm wiling to give up 75m on this dipole, wondering if 40 or 20 is hurt; and hoping for better 15m against all the full size variants.

A G5RV is a good 4 band antenna (80m, 40m, 20m, and 12m). A ZS6BKW is a good 5 band antenna (40m, 20m, 17m, 12m, and 10m).

A G5RVjr is a good 3 band antenna (40m, 20m, and 10m). A ZS6BKWjr should be a good 2 band antenna (20m and 10m).

Neither works very well on 15m.

However, my ZS6BKW does load on 80m through my MFJ-949E. EZNEC says it has a 50 ohm SWR of 13:1 on 3.75 MHz with an SWR on the ladder-line of about 35:1. I would use it as an emergency antenna for 80m if I needed to.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
LA9XSA
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« Reply #2 on: December 11, 2012, 02:24:59 PM »

What is even a ZS6BKW jr? Wouldn't that mean taking a G5RVjr, and taking it through a computer modelling process to improve its match over a G5RVjr, presumably adding 12 or 17 meters to the G5RVjr? After, all the idea of the ZS6BKW is to improve the G5RV so it matches 50 ohm coax on more than one band, and is easily tuned on others - unlike a G5RV which is supposed to connected to a balanaced line tuner on all bands?
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W5DXP
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« Reply #3 on: December 12, 2012, 06:07:57 AM »

What is even a ZS6BKW jr?

It's a half-sized ZS6BKW that nobody uses.Smiley It would cover 20m and the FM part of 10m (according to EZNEC).

Quote
- unlike a G5RV which is supposed to connected to a balanced line tuner on all bands?

Most standard G5RVs use ~30' of twinlead for a series matching section, coax the rest of the way to the shack, and driven through an unbalanced tuner. A 1:1 choke-balun should be installed at the twinlead/coax junction.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
W5JON
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Posts: 167




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« Reply #4 on: December 12, 2012, 07:34:21 AM »

Hi,

I have used a ZS6BKW for several years and am very pleased with it's 6-40m performance. This should shed some light on the subject.  When compared to a G5RV it seems the performance of a ZS6BKW is a well kept secret.

http://www.w5ddl.org/files/Zs6bkw_vs_G5rv_20100221b.pdf

73,

John  V47JA  -  W5JON


 
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LA9XSA
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« Reply #5 on: December 12, 2012, 06:24:22 PM »

It's a half-sized ZS6BKW that nobody uses.Smiley
I see - nobody should be using that.
It would cover 20m and the FM part of 10m (according to EZNEC).
What if you take a G5RVjr and vary the open wire feed and top length until you find a combination that actually covers more bands than a G5RVjr; that would be as close to a true ZS6BKWjr as you'd get, in my opinion, if one such combination even exists.
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W5DXP
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« Reply #6 on: December 12, 2012, 07:42:20 PM »

What if you take a G5RVjr and vary the open wire feed and top length until you find a combination that actually covers more bands than a G5RVjr;

A G5RV works well on 80m, 40m, 20m, and 12m. So a G5RVjr works well on 40m, 20m, 10m, and 6m.

A ZS6BKW works well on 40m, 20m, 17m, 12m, and 10m. So a ZS6BKWjr works well on 20m, 10m, 8.5m, 6m, and 5m.

Since 8.5m and 5m are not ham bands, it should be obvious that a G5RVjr is superior to a ZS6BKWjr.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K8AG
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Posts: 352




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« Reply #7 on: December 13, 2012, 01:11:02 PM »

I have been using a ZS6BKW for well over a decade now.  It is my favorite antenna.  But I think if you like 80M and even 40M a lot, a G5RV jr might be better.  My tuner struggles on 80M.  I can operate.  But when an auto tuner is having trouble you know the efficiency can't be all that great.

Thought about building one for portable use.  Instead I created an OCFD that works well with my 40, 30, 20 PFR-3.

My 2 cents.

73, JP, K8AG
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LA9XSA
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« Reply #8 on: December 13, 2012, 01:37:40 PM »

W5DXP, I didn't say cut the ZS6BKW in half. I said put G5RVjr-sized ladder line fed doublet into EZNec and play around with the lengths.
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W0BTU
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« Reply #9 on: December 13, 2012, 09:24:07 PM »

I'd like someone else to try the W0BTU Antenna and tell me what they think.
http://www.w0btu.com/g5rv_antenna.html#w0btu_antenna
It covers more bands than either the G5RV or the ZS6BKW.
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W5DXP
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« Reply #10 on: December 14, 2012, 05:56:20 AM »


My ZS6BKW wound up with close to those dimensions. When you tap the ladder-line at 31', do you let the remaining 8.5' portion of the ladder-line hang open circuited? Or do you switch out that 8.5' portion? Or do you simply short the old feedpoint to the new feedpoint? A schematic of that switching circuit would be nice.

Yesterday on 80m, I was messing with my ZS6BKW (94' insulated wire dipole, 38' of The Wireman #554). It has a 10 ohm resonant impedance on 3.5 MHz for a minimum SWR on 80m of 5:1 on 3.5 MHz and much higher on 4 MHz. From the resonant 3.5 MHz frequency to 4 MHz, the feedpoint resistance goes up along with the inductive reactance. If we pick a frequency between 3.5 MHz and 4 MHz and neutralize the inductive reactance at that point, we will improve the resonant frequency and the SWR. I tried a 500 pf series doorknob capacitor on the coax side of my choke-balun and got an SWR of 2:1 on 3.86 MHz. Since my SG-500 amp is spec'ed to work into a maximum SWR of 6:1, I am now in good shape on that part of 80m. I checked into a roundtable on 3.87 MHz and got S9+10 reports from Arkansas. Here's a picture of the doorknob capacitor. I'm going to put it in a box with an in/out switch.

http://www.w5dxp.com/DoorKnob.JPG
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
W5WSS
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Posts: 1745




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« Reply #11 on: December 14, 2012, 06:19:51 AM »

Hello Cecil, I have two 500pf @ 20kv I might try that using one in series on an indoor vertical dipole antenna I just built.

Perhaps inserting it up below the top hat.
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W3KC
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Posts: 23




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« Reply #12 on: December 14, 2012, 07:31:01 AM »

Excellent result Cecil. If it could be tamed in a similar fashion on 30 and 15 by switching in a lumped reactance at the ladder line / coax transition point, a simple 4 way (through, 80, 30, 15) remote switch could make it into a minimal fuss 80 thru 10 meter setup.
I really like my ZS6BKW.  My tuner (Cubic ST3B) is able to tune it at the coax end in the shack on 80, 30, and 15 so that it performs well as an all band antenna, but taming it remotely would seem to be a better setup (faster bandswitching at least).

73 Chas
« Last Edit: December 14, 2012, 07:33:38 AM by W3KC » Logged
W0BTU
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« Reply #13 on: December 14, 2012, 12:09:33 PM »


When you tap the ladder-line at 31', do you let the remaining 8.5' portion of the ladder-line hang open circuited? Or do you switch out that 8.5' portion? Or do you simply short the old feedpoint to the new feedpoint? A schematic of that switching circuit would be nice.

The remaining 8.5' section is not connected in any way on 80 or 15. It must be totally removed from the feedline. If one end of it is left connected, the antenna doesn't work right.

I need to fix the way I describe it there. It implies otherwise.

EDIT: I've never tried shorting the 8.5' piece as you asked.
« Last Edit: December 14, 2012, 12:24:40 PM by W0BTU » Logged

W5DXP
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« Reply #14 on: December 14, 2012, 12:48:26 PM »

The remaining 8.5' section is not connected in any way on 80 or 15. It must be totally removed from the feedline. If one end of it is left connected, the antenna doesn't work right.

Occasionally, leaving that piece of ladder-line connected as a shorted or open stub actually helps with the matching and adds a whole other dimension to the concept of "matching". I'm determined to figure out all this stuff before I kick the bucket.Smiley
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
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