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Old 6th Aug 2022, 4:08 pm   #1
G6Tanuki
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Default G5RV on 5MHz?

Has anyone got experience of getting a full size G5RV antenna to work on 5.3MHz??

A friend has a G5RV he uses on the upper HF bands and (it must be said with less than impressive results on 3.5MHz) but I am going to loan him one of my PRC320 radios so he can have a go on 5 MHz SSB.

Will it work?? The PRC320 antenna matcher will deliver RF into some crazy mismatched loads.. So I am not worried about damage to the radio, but "will it radiate?"
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Old 6th Aug 2022, 8:03 pm   #2
Sparky67
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Default Re: G5RV on 5MHz?

I looked into this a few years ago and came across THIS article on the G5RV’s performance across HF. It indicates the impedance at the end of the ladder line section will be pretty horrendous at 5MHz and that’s where the ATU should be placed, rather than expecting it to match any random coax length (via a balun) to the transmitter ATU. It also indicates there would be noticeable associated losses in the coax due to the very high VSWR.

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Old 7th Aug 2022, 7:45 am   #3
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Default Re: G5RV on 5MHz?

I have used a G5RV on 5317 together with a modified KW Valiant and an MFJ tuner or a KW107 and received good reports, depending on conditions of course.
I know nothing about the PRC320 though.
Don m5aky
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Old 7th Aug 2022, 6:10 pm   #4
G6Tanuki
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Default Re: G5RV on 5MHz?

Looking at the link from Sparky67, it seems that the G5RV is a no-go; in this particular scenario it would involve putting an antema-matcher between the end of the ladder-line and the ongoing coax but it would need to 'float' somewhere around 15 feet in the air!

Given the seeming uselessness of the G5RV in my friend's case, we are now seeking other paths; he has told the community-group of his 'bungalows exclusively for the over-50s' that he intends to erect a "Flag-mast, 33-feet, white" in his back garden, and intends to use it to fly "the Union Flag, or, as is chrioinologically-appropriate, Naval Pennants and Ensigns".

[He's an ex-Naval rather-senior-officer, ... ]

The flag-mast is of course 'conveniently' 1/4-wave on 7MHz and with a suitable coil-in-a-tupperware-box can be base-loaded to work on 60 and 80 Metres.

I wonder what the neighbours will think when myself and his two sons descend on the property and use spades to 'slit' the lawn to install a frw hundred metres of scrap T&E mains cable to provide radials?

Still, I hope it gets him back on-air reliably with his historic "R.L.Drake" 4-line radios [which don't do 5Mhz, hence the original question about using a PRC320]
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Old 7th Aug 2022, 9:54 pm   #5
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Default Re: G5RV on 5MHz?

Just to double-check I found a G5RV in the files supplied with the MMANA antenna modelling software so changed the feed impedance to 50 Ohms and had a look at the impedance and VSWR at the end of the ladder line where the coax attaches around 5.3 and 7.0 MHz. The radiation pattern for any RF reaching the top section is typical of a dipole fairly low to the ground in relation to the wavelength. Results, without any coax losses involved, are attached.

Martin
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Old 8th Aug 2022, 7:28 am   #6
G6Tanuki
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Default Re: G5RV on 5MHz?

Thanks Martin, those plots reinforced my belief that the G5RV would likely be about as efficient as a string of sausages at 5MHz.

It's not that brilliant on 7Mhz either... Somehow I have always thought of the G5RV as a compromise on all bands... But they seem strangely popular.
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Old 8th Aug 2022, 7:39 am   #7
M0AFJ, Tim
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Default Re: G5RV on 5MHz?

Have a look at the VK3ABQ variant, I’m going to try now when I get back off holiday
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Old 8th Aug 2022, 7:45 am   #8
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Default Re: G5RV on 5MHz?

Quote:
Originally Posted by M0AFJ, Tim View Post
Have a look at the VK3ABQ variant, Iím going to try now when I get back off holiday
Sorry, it should have read ZS6BKW variant
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Old 8th Aug 2022, 9:07 am   #9
Richard G4DYA
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Default Re: G5RV on 5MHz?

Quote:
Originally Posted by G6Tanuki View Post
I wonder what the neighbours will think when myself and his two sons descend on the property and use spades to 'slit' the lawn to install a frw hundred metres of scrap T&E mains cable to provide radials?
They might think, "They could have slit the lawn for those radials in half the time if they'd used a half-moon lawn edger instead of a spade!"
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Old 8th Aug 2022, 11:53 am   #10
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Default Re: G5RV on 5MHz?

I do not have a G5RV but a half one extended by a few feet at each end to fit between two trees. Ladder line down to an SGC auto tuner. It worked well enough on 5 MHz for the cadet NRN for a number of years until the plug was pulled on it.
Although the tuner will tune it on 80m it does not seem to radiate efficiently as although I hear stations they tend not to hear me.
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Old 8th Aug 2022, 12:32 pm   #11
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Default Re: G5RV on 5MHz?

I hadn't come across the ZS6BKW antenna before... Interesting!!! Though not really that appropriate in this case. My ancient ex-RN friend doesn't venture above 7.1Mhz and so antennas covering the upper HF bands at the expense of the lower aren't appropriate. Likewise anything needing a matcher dangling anywhere in the centre of the span.

The quarter wave vertical masquerading as a flag mast seems a pragmatic solution under the circumstances, and just maybe replacing the G5RV with an end fed wire...

Flag mast is on order, plan is to mount it as a tilt over using two lengths of white square plastic drainpipe cemented into the ground and the mast fitted between them.
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Old 8th Aug 2022, 1:50 pm   #12
Steve G4WCS
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Default Re: G5RV on 5MHz?

Ive just knocked together a W3EDP antenna inbetween decorationg, in an attempt to try something resonant instead of the ramdom length of wire going round the property. Its going to have to ho over the house roof to accomodate its length though.
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Old 8th Aug 2022, 3:16 pm   #13
G6Tanuki
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Default Re: G5RV on 5MHz?

Interesting to see that article proposing the "zeppelin" feed to the end of a half-wave element. Les Moxon's "HF Antennas for All Locations" has some less than complimentary things to say about the Zeppelin; basically it "cannot work" and only manages to achieve radiation by virtue of stray capacitance from the open leg to ground....
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