Unchained Preppers

Communications => Radio => Topic started by: JohnyMac on December 09, 2018, 12:57:29 PM

Title: A True Multi-band Antenna (80-10 Meters)
Post by: JohnyMac on December 09, 2018, 12:57:29 PM
I have been shopping for a new G5RV type antenna since Radio Works in VA. was sold. I currently have one running east-west (North south lopes) and I wanted one that goes north-south (west-east lopes). The new owner is focusing his production in a different direction than the G5RV right now. What it comes down to, is for me to make my own G5RV antenna.

Knowing that some of you are working on new antenna's over the winter I thought I would share this with the folks here.

Now many folks carry manufactured G5RV antenna's and market them as multi-band antenna's when in fact they are not. They are weak on 75/80 and 10-meters and will not pick up 60, 30, and 15 meters. Eventually my search lead me to reading an article entitled, The Truth about the G5RV Antenna (http://www.w0btu.com/g5rv_antenna.html).

The article spoke to two different versions of the G5RV antenna - The ZS6BKW and W0BTU Antenna's. As it is tough in life to get an all encompassing piece of equipment ala "getting your cake and eating it too", both the ZS6BKW and W0BTU antenna's are an improvement over the G5RV antenna however, neither one is all encompassing.

Because I hate wasting my time, and prefer doing something once rather than twice, I contacted Cecil Moore, W5DXP who has reportedly made some considerable improvements to the ZS6BKW and W0BTU antenna's.

Moore and I have been trading emails over the past few months and he just published an article entitled How to Transform Your ZS6BKW Into an All-HF-Band Antenna (http://www.w5dxp.com/ZS6BKW80/ZS6BKW80.HTM).

In essence the antenna is a dipole flattop 92' long with 39' of 450 ohm ladder line into a 1:1 choke-balun to 50 ohm coax. If you just did this your SWR's (Standing Wave Ratio (https://en.wikipedia.org/wiki/Standing_wave_ratio)) would be the following in the following band's:

Meter      SWR
80           4.5*
60           >10**
40           1.4
30           >10**
20           1.3
17           1.4
15           >10**
12           1.2
10           1.6

If you don't want to have to use a tuner you really want to keep SWR below 1.5. If you use a tuner to control SWR lets say taming a high SWR, there is no tuner I am aware of that will bring an antenna's SWR down south of 2.0 if the SWR is north of 10.0.

*   You will need a tuner
** You can not tune

These results bring us to Option 1.

Option 1:

To bring 80-meters down to 1.2 SWR add a 500pf Doorknob capacitor*** post the 1:1 balun on the center coax center conductor. When you do this the SWR on 80-meters drops to around 1.2. The capacitor does not adversely affect SWR when left in line to 40, 20, 17, 12, & 10-meters.

*** Leaving the capacitor in line does not adversely affect the higher frequencies when you add ladder line as described in Option 2.

Option 2:

What can you do to optimize 40, 20, 17, 12, & 10-meters after adding the capacitor for 80-meters is to add/delete 450 ohm ladder line in 1 or 2-foot lengths. An easy way to do this without manually adding/deleting ladder line using banana clips, is to use a DPDT knife switch. By adding one or two feet to the existing 39-feet of ladder line helps SWR in the 40, 20, 17, 12, & 10-meter bands with the capacitor still in line.

Here are the SWR's for the following frequency's with an inline capacitor and by adding 1-2-feet of ladder line to the original 39-feet of ladder line via the DPDT knife switch.

Meters  SWR           Configuration
80         1.2                500pf capacitor & original 39' Ladder line   
60         >10**
40         1.5                500pf capacitor using knife switch add 1' ladder line
30         >10**
20         1.0                500pf capacitor using knife switch add 1' ladder line
17         1.4                500pf capacitor original 39' ladder line no additions
15         >10**
12         1.2                500pf capacitor using knife switch add 1' ladder line
10         1.8                500pf capacitor using knife switch add 2' ladder line

Option 3:

By using options 1 & 2 combined, SWR is great except for 60, 30, and 15-meters. Now we get into a bit more complicated procedure as it involves a couple more knife switches, a relay switch, and some additional capacitors (60-meters a 128pf, 30-meters 104pf, 15-meters  44.5pf). If you execute on this last procedure you will in fact have a true multi-band antenna from 80-10-meters.

This is what the SWR looks like for 60, 30, & 15-meters.

Meters  SWR             Configuration
80           1.2                Capacitor & original 39' Ladder line   
   60       1.5               Using knife switch add 2' ladder line PLUS using relay switch add 128pf capacitor
40           1.5                 Using knife switch add 1' ladder line
   30       1.1               Using knife switch add 2' ladder line PLUS using relay switch add 104pf capacitor
20           1.0                Using knife switch add 1' ladder line
17           1.4                Original 39' ladder line no additions
  15        1.0               Original 39' ladder line PLUS using relay switch add 44.5pf capacitor
12           1.2                Using knife switch add 1' ladder line
10           1.8                Using knife switch add 2' ladder line

Please take the time to read both articles as they do much more justice than my short explanation does complete with PICTURES and GRAPHS.

With deer season ending for now, and my outside projects coming to a close do to weather, I will build this antenna and document all of my moves. Once done I will hoist and let you know how it works.



Title: Re: A Tue Multi-band Antenna (80-10 Meters)
Post by: pkveazey on December 09, 2018, 06:40:06 PM
I've built and tried a bunch of antennas and I have found that the G5RV is kind of hit and miss. Some people have good luck with it and a lot of others would do better with connections to the roof gutters. I bailed out on all that stuff and put up a 160 meter dipole and use an autotuner and its the best thing I've tried that covers everything. Its a little bit flakey on 80 meters so I use a 7 foot tall 80 meter Hamstick at 30 feet up and it works perfectly.
Title: Re: A True Multi-band Antenna (80-10 Meters)
Post by: Jackalope on December 12, 2018, 04:17:36 PM
    Well, as noted in the cited websites, the original G5RV is a compromise antenna which doesn't have outstanding performance on any band.  If you're going use a modified G5RV or ZS6BKW, I'd suggest keeping it as simple as possible.  Your option #1 is the simplest.  I would avoid using the switches as suggested in the one article.  It wouldn't be any fun going out in the darkness, or a snowstorm to change the switch position.  I've never been too impressed with the durability of antennas which use ladder line.

    I like simple dipoles.  But I'm also a fan of the W3DZZ multi-band trap dipole.  It's a design from the 1950's, and it's well tested.  Unadilla-Reyco produced the traps and the balun for the antenna, and these can still be found used on line.  I used that model of antenna and a Kenwood TS-120S 100 watt transceiver to get DXCC, so I know it works well.  Here's a website that goes into detail regarding the dimensions and how to produce your own traps: https://rsars.files.wordpress.com/2013/01/w3dzz-antenna-iss-1-31.pdf

    At my new QTH, there are plenty of trees, so there should be lots of opportunities to try out different antennas.  My biggest problem is getting the antenna wires up to where I'd like them to be.  I'll be investing in an antenna launcher, so that should solve the problem.

    Anyways, we'll be looking forward to seeing how your experiment progresses.  Please do let us know the results.
Title: Re: A True Multi-band Antenna (80-10 Meters)
Post by: JohnyMac on December 12, 2018, 07:29:24 PM
Great article Jackalope. You know my setup here and I can do all of the knife switch/relay's inside so no snow to worry about ;-)

As you point out, UV helps greatly for Ladder Line breakdown. With that written, and the antenna works well maybe a change in LL every other year is appropriate.

Good discussion. :cheers:
Title: Re: A True Multi-band Antenna (80-10 Meters)
Post by: Jackalope on December 13, 2018, 03:42:39 AM
  That's a good point regarding making changes every other year.  Considering that the components are exposed to the elements continuously, it may be a very good idea to at least give a good examination on a biennial basis.  I've had coax cable last over 10 years, but there must be some degradation of the dielectric between the core wire and the shield.  Depending upon where you put the antenna, it'll get some shade from your high trees, which should help with longevity.  Oh yeah, don't go with the solid wire ladder line sold on ebay, but go with the multi-stranded ladder line, it'll last much longer and it'll survive ice storms much better.