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 Need Help with a problem Comet H422 
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Post Need Help with a problem Comet H422
Need some suggestions to try, as this is driving me mad......

It has a Good SWR and bandwidth on 10 MTRS and is 2:1 from around 27.8 to 29.9, supposed to be 2:1 from around 28.1 to 29.6....this is set to the middle setting on the Instructions.

But all the other bands are not working....
15M(21Mhz) is 3:1 across the band and there is a dip down to around 1.5:1 at 19.9 Mhz
20M(14Mhz) is 5:1 across the band and there is no dip anywhere.
40M(7MHz) is 10:1 across the band with no dip anywhere.

I have stripped all the traps down and they look like new.....no dirt, burning not even discoloured.
This is the newer version which has rivets on the dust caps, rivets on the outer capacitance cover but through bolts on the trap wire.
I have put all new rivets in it, tried 2 different lengths of cables and 2 different baluns and still get the same results.
Does anyone know on the off chance, how many turns the 10M trap should have, as at the moment its like the trap has gone faulty, but there are no visual defects, wondering if maybe i have got some sort of factory defect one.
I had one of these before and it went bad on 40MTRS but that was down to corrosion on the joints, but i've cleaned all joints on this one and still no joy.

There is no reason that i can see for it not to work...

Am i missing something obvious.


Any Help much appreciated.

Cheers...Chris


Thu Sep 09, 2021 8:53 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
Measure resistance of traps and antenna sections with meter probes both ways round. If different resistance with leads swapped then bad connection.

Also check traps are in correct order.

As the shortest wavelength is working it sounds line the connection to first trap is the problem or trapsnin wrong order.

Also measure pairs of traps for same resistances and inductance.

There should be almost zero ohms from tip to connection of the assembled antenna.
EDIT : last sentence may not be entirely true depending on type of trap.

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Thu Sep 09, 2021 11:02 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
M1MPW wrote:
Measure resistance of traps and antenna sections with meter probes both ways round. If different resistance with leads swapped then bad connection.

Also check traps are in correct order.

As the shortest wavelength is working it sounds line the connection to first trap is the problem or trapsnin wrong order.

Also measure pairs of traps for same resistances and inductance.

There should be almost zero ohms from tip to connection of the assembled antenna.


Thanks for the reply....
Already tried that.....
My meter leads are 0.2ohms together and i get 0.3 on all parts of antenna, both ways across traps....even tried on the Buzzer/diode setting and get a buzz both way's.
With the H422 you cant get the traps in the wrong order as it only fits one way.

Thanks chris


Thu Sep 09, 2021 11:08 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
https://tinyurl.com/rszyxrmw

This is the 10MTR trap and all the others are in the same condition.


Thu Sep 09, 2021 11:12 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
Link does not work, just gets a 404 error

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Fri Sep 10, 2021 6:11 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
Another option is connect a 50ohm resistor across the output of the balun and check swr.
Should be 1:1 across all bands.

Connect 50ohm across end of coax and check swr.

This should rule out baluns and coax hopefully

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Fri Sep 10, 2021 11:00 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
M0DUH wrote:
Link does not work, just gets a 404 error


Thanks for that, will have to try and sort it when I get home, not very good at this internet stuff and posting pics.


Sun Sep 12, 2021 3:13 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
M1MPW wrote:
Another option is connect a 50ohm resistor across the output of the balun and check swr.
Should be 1:1 across all bands.

Connect 50ohm across end of coax and check swr.

This should rule out baluns and coax hopefully


I don't have a 50 ohm resistor, but I do have another balun which I have tried and still the same and I did put a dummy load at the end of the cable to rule that out.

Cheers


Sun Sep 12, 2021 3:15 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
I'd go with one of the inboard traps being faulty.
have you got a GDO, or an analyzer you can press into service as a GDO?

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Sun Sep 12, 2021 5:09 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
bonehead wrote:
I'd go with one of the inboard traps being faulty.
have you got a GDO, or an analyzer you can press into service as a GDO?


No, don't own such a thing, all I have is a multimeter.


Mon Sep 13, 2021 10:56 am
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
Try the 10Meter trap pic again.
All the traps look in the same condition as this one.


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Mon Sep 13, 2021 2:26 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
Just a thought... Try the ariel without a balun.

Also , you have a 50ohm resistor if you have a dummy load.
Use short lengths of wire from the dummy load to the baluns. Maybe using croc clips or just wrapping the wire tightly round connections .
If SO239 socket, a 4mm banana plugs works fine.

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Tue Sep 14, 2021 9:21 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
M1MPW wrote:
Just a thought... Try the ariel without a balun.

Also , you have a 50ohm resistor if you have a dummy load.
Use short lengths of wire from the dummy load to the baluns. Maybe using croc clips or just wrapping the wire tightly round connections .
If SO239 socket, a 4mm banana plugs works fine.


Gonna try and get out there saturday and have another play with aerial....
Will give that a try with the Dummy load.....i also have another couple of 1:1 baluns i will try, just in case.
Tried it without the balun and there was not much difference, which is why i was thinking a trap has gone faulty, but the traps look like new.


Thanks.


Wed Sep 15, 2021 4:44 am
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
chrised wrote:
It has a Good SWR and bandwidth on 10 MTRS and is 2:1 from around 27.8 to 29.9, supposed to be 2:1 from around 28.1 to 29.6....this is set to the middle setting on the Instructions.

But all the other bands are not working....

Does anyone know on the off chance, how many turns the 10M trap should have, as at the moment its like the trap has gone faulty,


The fact that it tunes on 10m suggests the fault lies beyond the 10m trap, and that the 10m traps and balun/feed are all working.

The next traps are the 15m ones, have a look at these, if there's a fault here it'll throw out the reading on the other bands.

I feel for you, tracking these sort of fault down can be a right PITA. In my experience it's usually a poor joint somewhere.


Sat Sep 18, 2021 3:09 pm
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 Need Help with a problem Comet H422 
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Post Re: Need Help with a problem Comet H422
G0HVQ wrote:

The fact that it tunes on 10m suggests the fault lies beyond the 10m trap, and that the 10m traps and balun/feed are all working.

The next traps are the 15m ones, have a look at these, if there's a fault here it'll throw out the reading on the other bands.

I feel for you, tracking these sort of fault down can be a right PITA. In my experience it's usually a poor joint somewhere.


If i get a chance, i'm going to strip the 15M one down again and have another look.
I had a play friday with stripping the 10M trap again and disconnecting it from the 15M Element, but it never really proved anything, just made the 10M bandwidth even bigger.
I had less than 2:1 from 29.7 right down to 24.3.


Mon Sep 20, 2021 3:11 am
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