Alinco DJ-G7

In reply to MM0FMF:
Cheers for the link Andy

Will take a trip to local iron-mongers!!

73 Matt G8XYJ

In reply to G8XYJ:
Hi Matt
Old thread, new question - is this a 23cm antenna for £24?
If so, where from please?
Thanks
T!m
G4YTD

In reply to G4YTD:
Hi Tim

Im afraid they have been discontinued! I think I got mine so cheaply as I was buying alot of other gear and had the chance to haggle!! Plus Sandpiper may have been keen to shift them!

However all is not lost - take a look at Gerald G4OIG, Andy MM0FMF, Mine G8XYJ Flickr page - I am glad to report that I have joined the Bow Tie/ Quadruple Quad Revolution!! Excellent directionality as well as gain and F:B. Worth a look, if you need dimensions I can help - well worth making very lightweight.

Kindest Regards

Matt G8XYJ

In reply to G8XYJ:
Hi Matt
Thanks. I have sent you an e-mail to your QRZ account :slight_smile:

73

Tim

G4YTD

In reply to G4YTD:
Thanks Tim

I have just replied!!

73

Matt G8XYJ

In reply to G8XYJ:
Where did the SH770 come from?
I’ve found the Alinco antenna OK - certainly better than a larger whip (they call it a helical, but it isn’t) from Moonraker. That may have been OK on 2 / 70, but I only tested it on 23…

Will have a look at the bowtie - but I’d like to do a small cubical quad.

Cheers,

In reply to G4FUJ:

The reason I made a double quad, bowtie etc. was that they are very tolerant of measurement errors and therefore very tolerant of this fool with a hacksaw! The gain is quoted as 11dBi/8.85dBd for the bowtie so a small Yagi will soon outstrip it for gain, probably at about 5 or 6 elements. Constructional accuracy is important. I can remember seeing Ian White G3SEK (now GM3SEK) talking about building repeatable performance 70cms Yagi and he was filing elements to length and ISTR the accuracy needed being 0.5mm on 70cms. So it’s 3 times smaller on 23cms. The other advantage the double qaud has over a Yagi is that when horizontal polarised it has a very narrow vertical beamwidth but broader horizontal beamwidth. This means it is not critical peaking up the direction, ideal for on top of a windy hill.

The quadruple quad design that Roger MW0IDX and Ian(?)GW0VMW use on 70cms has 3dB more gain than the double quad and again is more tolerant of constructional tolerance than a Yagi although the balun requires careful attention especially as a scaled version for 23cms is getting a bit teeny tiny. Gerald’s implementation for 23cms looks exceptionaly well thought out for SOTA as it’s simple to deploy for vertically polarised operation which is the majority case for SOTA.

From personal experience, my double quad + 2m of cable is about 4S points better on the DJ-G7’s S meter than the rubber duck. I’m sure it isn’t 24dB better really!

Andy
MM0FMF

In reply to MM0FMF:
Thanks Andy.
I guess even a file is going to be a trifle rough for 23cm beam then. Fine grade wet and dry anyone? ;o)
I shall take a closer look at the double quad / bowtie - have several links somewhere.
Season’s Greetings from Cheltenham.
Graham G4FUJ

In reply to MM0FMF:

Constructional accuracy is important.
Yes, but …

Ian White G3SEK (now GM3SEK) talking about building
repeatable performance 70cms Yagi and he was filing elements to length
and ISTR the accuracy needed being 0.5mm on 70cms. So it’s 3 times
smaller on 23cms.
Well, the elements on my home brew 23cm Yagi are no more accurate than 0.5mm and it works fine.
Ditto for my home brew 13cm Yagi, where 0.5mm is still less than 0.4% of the wavelength.

So I don’t think it’s as critical as Ian says for 70cm; and anyway 0.5mm is easy to do with a hacksaw on 4mm or 6mm elements.

What’s important is that the lengths you are aiming for are correct and measured accurately - i.e. make sure you follow the design carefully - for both the antenna and the balun!

I must admit I’d like to try Gerald’s quad for 23cm and do a comparison with the Yagi. Certainly, as always, a decent antenna makes a huge difference.

PS the “bowtie” is certainly an excellent broad beamwidth antenna (though again best with a balun) - it makes a superb feed at 23cm for my portable 2m dish and seems to illuminate the dish nicely!

73
John GM8OTI

In reply to G4FUJ:
Hi Graham

Thanks for chasing me today! I could not hear you on 4m however I still put some 23cm calls out in the general direction of Cheltenham.

The RH770 was from a seller on Ebay for around 20 pounds.
Despite this without a doubt the bow tie or Quadruple Quad seem to be the best compromise when it comes Performance:Weight!

Many thanks again

Matt G8XYJ

In reply to G8XYJ:
My 4m vertical is screened by two other antennas in that direction Matt.
I did have the beams inc. 23cm Sandpiper circular pointing in your direction, but also had to pay a visit to friends I haven’t seen for a while, so couldn’t hang about too long, unfortunately.
Graham, G8XRS, has a 4m vertical higher, and out in the clear (compared to mine) - heard him working you.
Driven element on my 2m Tonna beam needs refitting (darn pigeons) - time for a stonger and perhaps better performing beam at the top of the mast! :o)
Noted on RH770 - will just have to keep an eye out for something better for the DJ-G7.

73
Graham G4FUJ