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SWR issues with more power..
- Thread starter CB590
- Start date
S&W357
$upporting Member KO4RJD....WDX-556
I don’t know. I had an original Starduster years ago. Great antennas. If/when I replace my A99 it will probably be with a Starduster wannabe.
Got the proper 6AWG solid wire from mast to the ground rod.
I do 'hear' you about the white wire not doing squat for the rig/amp. Would not having a ground from the rig/amp to the ground rod be a better idea in case of a lightning hit (if I disconnect the antenna coax like I usually do) to avoid lighting coming back via the little white wire??
Anyone think removing the choke up top by the feedpoint on the antenna may help reduce the SWR reading??
I do 'hear' you about the white wire not doing squat for the rig/amp. Would not having a ground from the rig/amp to the ground rod be a better idea in case of a lightning hit (if I disconnect the antenna coax like I usually do) to avoid lighting coming back via the little white wire??
Anyone think removing the choke up top by the feedpoint on the antenna may help reduce the SWR reading??
So I took the 1:1 MFJ choke out..
Keep in mind this is a metal mast.. sister said I'm barely making static on the radio.. which is a good thing
SWR went way down by over a full 1..
On medium I get like 1.3
On high I get like 1.5
The power side of the meter swings up when modulating on AM a bit (like 15-20w) vs the backwards swing it was doing.. the SWR climbs also a tiny bit like 0.2 - 0.3 on AM..
DK Medium power AMP on..
DK High power AMP on..
Keep in mind this is a metal mast.. sister said I'm barely making static on the radio.. which is a good thing
SWR went way down by over a full 1..
On medium I get like 1.3
On high I get like 1.5
The power side of the meter swings up when modulating on AM a bit (like 15-20w) vs the backwards swing it was doing.. the SWR climbs also a tiny bit like 0.2 - 0.3 on AM..
DK Medium power AMP on..
DK High power AMP on..
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I also noticed when I zip tied the coax to the mast I had a rise then drop. The readings above were with the coax dangling outwards..
So I cut the zip ties and made a simple pvc standoffs about 6"..
The SWR no longer rises first and then drops.. just a solid DK SWR till I modulate then is rises slightly as previously noted.
I did go back thru old forum posts back to 2006 when A99 and GPK came up and coax related things.. this prompted all these tests today.
Needless to say with the AMP off my SWR is flat..
So I cut the zip ties and made a simple pvc standoffs about 6"..
The SWR no longer rises first and then drops.. just a solid DK SWR till I modulate then is rises slightly as previously noted.
I did go back thru old forum posts back to 2006 when A99 and GPK came up and coax related things.. this prompted all these tests today.
Needless to say with the AMP off my SWR is flat..
BJ radionut
Supporting Member and 6m addict
I had an swr issue with low power yesterday. The ol' skipshooter hit too many trees. Solved my intermittent rx problem too.
No spring. My 6ft failed so I put the 7ft back on. The rubber was damaged at the top and some of the coil exposed. I'm assuming water got in there and caused some corrosion. Either that or a piece of the wire was broken inside. As the antenna moved the swr would go from flat to hitting the peg.
I only drive that truck about once a month. I've been noticing an intermittent problem where there is no noise level. If I key up and unkey the receiver would come back. I thought I had a radio problem but it was the antenna.
what is happening is, your coax is resonating with your antenna. your length of coax is wrong! In other words your coax is adding an impedance to your antenna and then you are trying to compensate for the impedance by adjusting the rings on the antenna. which makes your antenna and your coax 50 ohms at the the point where the coax meets your swr meter!
Try this,
disconnect your coax from your antenna and swr meter.
place a "T" at the output side of your swr meter
one side of your "T" connect the coax that goes to your antenna (but do not connect it to the antenna)
on the other side of the "T" place a 50 Ohm dummy load directly to it! (NO JUMPER between the "T" and the dummy load!!)
WITH THE AMP TURNED OFF!!!
key your radio. look to see if you have an swr on your meter.
What this will show you is how much of an affect your coax has on a 50 Ohm load.
If you do, then the coax is not cut to the resonant frequency of operation.
You now need to start trimming the antenna side of your coax to the point where your swr meter shows no reflect/swr!
this is best done with a broad frequency transmitter.
what you are looking to achieve is, that you have an even swr reading based of the center frequency of the band of operation.
Now that your swr meter shows a VSWR Dip at the center frequency at the band of operation, install the new connector, remove the t and dummy load, reconnect your coax to the swr meter and the antenna and retune your antenna.
doing this will guarantee that the antenna itself is 50 ohms.
your swr meter will not see the coax as adding an impedance to the antenna.
the RF will radiate from the antenna and not the coax and the antenna.
the only thing that the coax will have an affect on the station is DB LOSS, which comes down to quality of coax.
This is also necessary with jumpers between your equipment too.
if anyone wants the technical explanation let me know. I'll be happy to provide it. with experiments that you can do to prove yourself.
Noticed how i never mentioned a particular frequency because this works for all mono band stations at all frequencies throughout all bands but is not necessary at microwave frequencies!
I hope this helps
I hope to hear you on the air when mother nature allows it
707
with that friendly 5,
one more time,
bye, bye, bye!
Try this,
disconnect your coax from your antenna and swr meter.
place a "T" at the output side of your swr meter
one side of your "T" connect the coax that goes to your antenna (but do not connect it to the antenna)
on the other side of the "T" place a 50 Ohm dummy load directly to it! (NO JUMPER between the "T" and the dummy load!!)
WITH THE AMP TURNED OFF!!!
key your radio. look to see if you have an swr on your meter.
What this will show you is how much of an affect your coax has on a 50 Ohm load.
If you do, then the coax is not cut to the resonant frequency of operation.
You now need to start trimming the antenna side of your coax to the point where your swr meter shows no reflect/swr!
this is best done with a broad frequency transmitter.
what you are looking to achieve is, that you have an even swr reading based of the center frequency of the band of operation.
Now that your swr meter shows a VSWR Dip at the center frequency at the band of operation, install the new connector, remove the t and dummy load, reconnect your coax to the swr meter and the antenna and retune your antenna.
doing this will guarantee that the antenna itself is 50 ohms.
your swr meter will not see the coax as adding an impedance to the antenna.
the RF will radiate from the antenna and not the coax and the antenna.
the only thing that the coax will have an affect on the station is DB LOSS, which comes down to quality of coax.
This is also necessary with jumpers between your equipment too.
if anyone wants the technical explanation let me know. I'll be happy to provide it. with experiments that you can do to prove yourself.
Noticed how i never mentioned a particular frequency because this works for all mono band stations at all frequencies throughout all bands but is not necessary at microwave frequencies!
I hope this helps
I hope to hear you on the air when mother nature allows it
707
with that friendly 5,
one more time,
bye, bye, bye!
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the other problem your having with forward swr swing with forward power on modulation is. Your RMS watts on a dead key is different than your RMS watts with modulation.
try this,
with the amp off raise the dead key of your radio and check your SWR.
now check the SWR when you modulate.
you wont see that much of a drastic difference. that because your dead key watts and modulated watts are almost the same. it is more drastic when you lower your dead key watts to 1 watt dead key and you swing up to 6 watts than having your radio set to a 4 watt dead key and swing up to 6 watts. so if your radio has a lot of rms swing then your true swr would be the modulated swr and not your dead key swr. unless you like to plug ears with dead keys then that would be your true swr. for the simple fact of how you operate your station. a radio with lots of rms swing coupled with a poorly tuned station will give you the results you are currently having along with a bald spot from ripping out your hair.
try this,
with the amp off raise the dead key of your radio and check your SWR.
now check the SWR when you modulate.
you wont see that much of a drastic difference. that because your dead key watts and modulated watts are almost the same. it is more drastic when you lower your dead key watts to 1 watt dead key and you swing up to 6 watts than having your radio set to a 4 watt dead key and swing up to 6 watts. so if your radio has a lot of rms swing then your true swr would be the modulated swr and not your dead key swr. unless you like to plug ears with dead keys then that would be your true swr. for the simple fact of how you operate your station. a radio with lots of rms swing coupled with a poorly tuned station will give you the results you are currently having along with a bald spot from ripping out your hair.
This is one way to find an electrical 1/2 wavelength multiple, that is all. If this fixes your issue then your antenna, at best, is a flawed design. Also, a well placed (not always at the feed point) choke will work just as well to resolve this problem, as generally will a set of near 1/4 wavelength radials...
Fun fact. If to take the directions above, and replace the open circuit on the end of the feed line with a short circuit, this method will let you find the odd 1/4 wavelength multiples. Anyone want to take a stab at why both of these work?
The DB