High VSWR on 432 MHz


g4zod@btinternet.com
 

Good morning all.

Thank you all for your helpful feed back.

It is interesting that I can still hear the Beacon PI7CIS with my mast down. (and I am in Greater London) This seems to indicate that the Coax is still connected to the Antenna.

The last time I dropped the Scam Mast to change the seals and worked on the various Yagis, I found when we heaved the mast up, the VSWR had gone up up on the 70CMs Yagi .

What is interesting is that the VSWR goes up and down slightly depending on which meter I use to test it. ( But I can understand why I get these variation) (I did use a Bird Meter with a 800 MHz slug and it gave me a VSWR reading of about 3-1.)

It seems that my new radio senses a higher VSWR then all my other stand alone meters.

Until HMG and Boris ease the the restrictions sufficiently to get a "Working Party" around to my house I will stick to my 70Cms Colinear.

Thank you for the advice about the possible use of a suitable ATU. I think I will shelve the idea.

The good news is the my 2 Metre 5 element MET and 23 CMs 14 over 14 Tonna which have been on my mast for 28 Years are still working perfectly, so I can still get some contacts.

Julian G4ZOD



Tony G4NBS
 

Hi Julian
 
Many years ago I had a problem with water in coax on 23cms - strangely it made little difference to my Rx performance but the SWR was rather high and not a lot of it actually got radiated!

What happens if you put a short patch lead in line? I would guess that would alter the SWR the rig sees and might help explain why it sees worse than your SWR meter?
I'm inclined to agree with others that the problem might be worse than you suspect but might prove it either way.........

Good luck
73
Tony G4NBS 


Andy GD1MIP
 

Julian G4ZOD,  you said..... 'It seems that my new radio senses a higher VSWR then all my other stand alone meters'

My interest was caught. What radio do you have?  I have an IC9700,  that shows a higher SWR on 70cm and 23cm than my stand alone meters or antenna analyser,  eg 1.2:1 on analyser shows 2:1 on radio display. 

Andy Morgan GD1MIP 


Gordon REASON <gordonj.reason@...>
 

If , you have a good modern oscilloscope , then why not build the cheap TimeDelay 'thing' , using a 74AC14

hex Shmitt trigger IC . it's on Youtube ...........

Just connect to the end of your Coax cable , and it will tell you if the problem is a short or open , and with some simple maths , how far along the coax , it is .........

On 17 February 2021 at 10:29 Andy GD1MIP <gd1mip@...> wrote:

Julian G4ZOD,  you said..... 'It seems that my new radio senses a higher VSWR then all my other stand alone meters'

My interest was caught. What radio do you have?  I have an IC9700,  that shows a higher SWR on 70cm and 23cm than my stand alone meters or antenna analyser,  eg 1.2:1 on analyser shows 2:1 on radio display. 

Andy Morgan GD1MIP 


Julian G1EKW
 

Also, further to Gordon's reply, if you have access to one, I find the nanoVNA V2 to be pretty good at sussing out coax problems and its time domain/delay function is very useful for this.

Julian Grammer. G1EKW