SIRIO sy27-4 yagi keep the gama match or convert to hairpin , Thoughts ? experience ?

[Geoexplorer69]

Well sad news .
Went to re check everything as the new coax didn’t come in today. Using the exact same equipment from yesterday the swr jumped up to 2.3 across the entire portion of the band I had set yesterday.

I fooled around with the gama match and could only get the swr down to 1.3-1 however something interesting happened as the X went to 0 but the R jumps up to 60 . The SWR moves between 1.4-1 and 2.0-1 across the Same bandwidth I had set up yesterday with great numbers. Here’s yesterday’s results…..

R=55 ,X =7 and an SWR of 1.1-1 to 1.2-1 from 26.975 to 27.700 it did move up to a 1.2-1 on up to 27.800 that was my stop point.

The antenna was not moved from where I had it yesterday and nothing was changed or damaged. I used the exact sam coax cable a new 20’ piece of rg58u low loss no kinks bends or damage .
It seem no matter what I change on the gama I can’t get back to the same numbers I had yesterday. Sh*t

Now the only thing that has changed is I did the measurements yesterday early morning while it was cooler , today I did the recheck afternoon and the temperature was hovering around 100 degrees. I still don’t think it’s going to matter that much.

Anyway I’m going to maybe look at shortening the elements as per the manual to set the middle at 27.000
Or 27.500 . I have everything set per the manual for 26.500 which is no cutting of the elements just use the existing pieces and the pre drilled holes and connectors.

I hope I can just maybe pull the screws out of the joints on the elements and move them then re drill new holes and secure the elements rather than cutting the ends down .

Any thoughts about the change in readings or re drilling
The elements rather than cutting off the ends ?

I’m all ears

Thanks

 

[Henry HPSD]

That is awfull...
I wish i was your neighbour so i could give a helping hand !

On the bright side...there is something "special" going on if you have other readings while not changing anything.
That sounds like "mechanical" failure somewhere.

First off all dont cut ..

Leave it to the factory settings, the stock factory settings of Sirio are good and spot on.
(and measure again and again to verify the lengths/distances are what they supposed to be)

Try to get your hands on a dummyload and insert that instead of the antenna.
And verify the coax and connectors.
While measuring move your coax around bend it a bit expecially at the plugs.
The SWR obvioulsy should not change.
If you dont have a dummyload.. maybe put the the coax on another working antenna.

Always looks for the 2;1 SWR marks...and write those down.
Reason: If there is additional loss somewhere... your bandwidth will become larger..
( PS Always write down the 2;1 SWR points... especially when you have it finally up in the air and working. You can verify your system over time by using that. That gives a better indication then the 1.1 values..)

Next thing is to set the VNA directly at the antenna and get the readings from that point. If you have the same SWR curve but the impedance is slightly higher witht X-0 ..I would still take the gamble and put it up.
Reason for that is ...youre initial measurment could have been the one with failure.
(Though i doubt that ...as it was exactly what EZNEC says it should be...but still..)
If the antenna is clear from all obstacles you should look for something that is say 55 Ohms.. 5 Ohms higher then the 50 Ohms.

Take extra precaution with the gamm-match.. is it moisty on the inside ?
im never a fan of matchingsystems as that is often the cause of strange behaviour and failure.

Whatever you do...Dont make any steps that cant be undone.

And if you have been bussy with it all day...step away... take a fresh look tomorrow.
SWR changes for a reason... although it may not look like it ...there has to be a cause.

Kind regards, Henry

 

[Geoexplorer69]

That is awfull...
I wish i was your neighbour so i could give a helping hand !

On the bright side...there is something "special" going on if you have other readings while not changing anything.
That sounds like "mechanical" failure somewhere.

First off all dont cut ..

Leave it to the factory settings, the stock factory settings of Sirio are good and spot on.
(and measure again and again to verify the lengths/distances are what they supposed to be)

Try to get your hands on a dummyload and insert that instead of the antenna.
And verify the coax and connectors.
While measuring move your coax around bend it a bit expecially at the plugs.
The SWR obvioulsy should not change.
If you dont have a dummyload.. maybe put the the coax on another working antenna.

Always looks for the 2;1 SWR marks...and write those down.
Reason: If there is additional loss somewhere... your bandwidth will become larger..
( PS Always write down the 2;1 SWR points... especially when you have it finally up in the air and working. You can verify your system over time by using that. That gives a better indication then the 1.1 values..)

Next thing is to set the VNA directly at the antenna and get the readings from that point. If you have the same SWR curve but the impedance is slightly higher witht X-0 ..I would still take the gamble and put it up.
Reason for that is ...youre initial measurment could have been the one with failure.
(Though i doubt that ...as it was exactly what EZNEC says it should be...but still..)
If the antenna is clear from all obstacles you should look for something that is say 55 Ohms.. 5 Ohms higher then the 50 Ohms.

Take extra precaution with the gamm-match.. is it moisty on the inside ?
im never a fan of matchingsystems as that is often the cause of strange behaviour and failure.

Whatever you do...Dont make any steps that cant be undone.

And if you have been bussy with it all day...step away... take a fresh look tomorrow.
SWR changes for a reason... although it may not look like it ...there has to be a cause.

Kind regards, Henry

Thank you Henry.
Well I don't think ill be cutting any of the radials regardless of what's happening
just might consider sliding them in and re- drilling some new holes if I have to shorten the elements for some reason . but for now I think ill do the following
1) Wait for the new coax to arrive, run the new coax on the nano to get an Idea if there are unacceptable losses and then recheck and adjust what's needed .

2) get this antenna up in the air and re check it again .

I did preform a check on the coax using the nanovna starting freq of 26.975 and ending freq of 27.800 and the results were a constant -0.71db at 26.975 and the same a 27.385 also -0.71db at 27.800 . I set the vna for those three points .

I don't have any moisture issues down here in the desert ( Yuma , Az ) .
so I think we can rule that out .

I have been thinking of purchasing a good dummy load but even if I order one it will take a week to get here . While Im not too impatient I am about to pull my damn hair out with this yagi lol.

one of the interesting things that did happen is the X went to 0 down from an X of 7 yesterday , and the R went up to 60 from 55 yesterday hmmmm that one really has me perplexed . if I did the simple math an R of 55 works out to a 1.1 to 1 or maybe an 1.1- .01 or .02 .

I will certainly be taking your advice and keeping track of the SWR marks and
Tomorrow I will take the nano vna and connect it directly to the antenna if possible I have several adapters but I'm not sure I have one that is sma to so239
I'll check ether way .
I do have a 1' LMR400 jumper I stupidly purchased not realizing it would be t stiff and short lol . maybe I can use that , your thoughts ?
anyway
Thank you again for all your help
I'll keep everyone posted
cheers
Roger

 

[Henry HPSD]

You can just buy a couple resistors online...that doesnt need to be high quality. You can verify the impedance with any multimeter.
I would recommend to get two 50 Ohms resistors. (not wire wound)
So you can place them in series...and end-up with 100 Ohms.
That way you can test either the 1;1 ...and the 2;1 marks on any SWR indicator.
(obviously dont put real power on them with your TRX unless they are capable of handling that).
Or perhaps..You might have some other relative low impedance resistor laying around in a junkbox? You can use that to verify the VNA..
In short... simple resistors are good enough for your VNA.

Sure...use the jumper... its about exclude possible causes.

Make sure the antenna is free from further obstacles.. if you turn the antenna and the SWR changes...you know there is near-by obstacle influence.

Just hang in there... you will get this solved.

 

[Geoexplorer69]

Ok a new day and some new tests

Got up this morning with the intent of getting this antenna tuned and the results were better than I expected so I don’t know what went on yesterday afternoon.

The only thing that I changed besides using the 1 foot LMR 400 jumper for the test at the antenna as I did change the L1 element length ( lower element of the Gama match / the L2 slider was used to adjust for low SWR ) back to as close to factory specifications as I could I don’t have a metric tape measure ( one is on order to save what’s left of my hair trying to convert a million decimal points) . I did actually change it a bit yesterday to play around with matching and today I realized that I hadn’t set it back .

However the numbers I got yesterday were taken with everything set to factory settings for 26.500 which in the Sirio manual says is no cutting of elements.

I dropped using the nanovna its screen is too small and almost impossible to read in daylight . I might get a bigger one later but it’s not in the cards for now. Although I have been entertaining the idea of a Rig expert .

I have ordered a dummy load as I feel Henry is absolutely right I need one .

So armed with my MFJ -259b and a freshly calibrated MFJ -226 I set to work the results are as follows ( note I used the 226 as a check of the 259b) ….

26.989 R= 64 X = 0 SWR = 1.2-1 interesting R63 = 1.2-1 swr ?
27.375 R=53 X=2-3 SWR=1.07-1
27.385 R=52 X=2 SWR=1.01-1
27.405 R=51 X=2 SWR=1.01-1
27.555 R=47 X=2. SWR=1.01-1
27.805 R=43 X=3 SWR=1.2-1 Interesting R 43 =1.2-1 swr ?

Everything jived with the 226 . I did raise the antenna up and the numbers started creeping up a little bit so I know I’ll have to do the final tuning when the new cable comes in.

Absolutely no elements were moved except for the L-1 on the Gama match set to factory and the L-2 slider of course was moved to obtain a low Swr as possible .

I will post again when everything is up and running.

Thanks to everyone for your support

Cheers, Roger

 

[Crawdad]

Although I have been entertaining the idea of a Rig expert .

You won't be disappointed....

I know these are evil, foul-smelling Amateur radio sites but excellent condition used RE's can be found for sale on QRZ, eHam, QTH.com. I got a pristine AA-55Zoom for $100 bucks less than new from an amateur on QRZ. Worth a look anyway.

7 3

 

[brandon7861]

Some of the older RigExperts did not allow OSL to the end of the coax without using a computer.

 

[Geoexplorer69]

Hello everyone,
This is the final chapter in the Sirio saga , lol
The new coax cable came in today while I was taking down the 5/8 wave Sirio antenna . So with the Yagi set up I unpacked the new coax and connected it to the yagi put it up on the poll halfway because that’s as high as my ladder will reach. I got a good but not perfect swr 1.3-1 from 26.975-27.800 the R and X values were acceptable 48 and 8 .

So I secured everything and raised the antenna up two more sections saving the last in case I had to fight the antenna back down to change anything.

Here ar my numbers now after raising the yagi up approximately 20’
SWR 1.23-1 , R 43.2 and the X is 2 . I think this is acceptable considering I’m using 75’ of RG 213U coax. I skipped the LMR 400uf for now because this is a temporary QTH setup. When I get to the permanent QTH I plan on using LMR 400 uf but I will need 125’ because of the distance between my tower and the radio room .

I’s been an adventure working with this antenna and conditions today are not great however I am receivingWWV clearly on 10m that's what I use to test the receive of my hf antennas .

I skipped the rotor for now so it;s going to be interesting having to run outside to twist the mast to point the beam .

Anyway thanks to everyone who has helped me with sound advice and some excellent encouragement.

Cheers
Roger

 

[brandon7861]

I think this is acceptable considering I’m using 75’ of RG 213U coax.

Good to know you got it up and working!

The way you worded the quoted part above makes me think you expected a worse SWR with that coax. The more loss the coax has, the lower the SWR reading will be. If you use a longer coax, SWR always goes down (unless you have CMC's) because less of the reflected power makes it back to the meter on account of the increased loss. Since the LMR400 has less loss than RG213, you might find that your SWR goes up a little when you switch to that coax.

 

[Geoexplorer69]

Good to know you got it up and working!

The way you worded the quoted part above makes me think you expected a worse SWR with that coax. The more loss the coax has, the lower the SWR reading will be. If you use a longer coax, SWR always goes down (unless you have CMC's) because less of the reflected power makes it back to the meter on account of the increased loss. Since the LMR400 has less loss than RG213, you might find that your SWR goes up a little when you switch to that coax.

Yes I guess I should have said I was hoping for lower lol , but yeah I .
well the Yagi is up Ive turned to get some real strong signals but as of yet I get absolutely no replies . Hmmm ?

That is interesting , I still get WWV booming in when I'm pointed in that direction
however I have made several CQ call's and not one answer even from stations that are coming in at 10-20 over on my radio . I checked the xmit on my radio by monitoring 27.385 and I'm transmitting fine I guess makes me wonder though .
heck I did better with the 5/8 ground plane lol .

anyway if you or anyone else has some ideas I'm all ears .

thank you
Roger