UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Closed Thread
 
Thread Tools
Old 5th Jul 2020, 11:01 am   #21
Gi4CZW Cliff
Pentode
 
Join Date: May 2011
Location: Enniskillen, Fermanagh, UK.
Posts: 188
Default Re: Static on antennas

Hello Mike and all. I had an issue with lightening and find this thread interesting.
Five IRF520's plus replacing them is a price. Flashing neon, when static high, would need you to be looking at the detector. I remember a static/lightening alarm circuit, but can't place it so far. Temp. solution is a double pole knife switch fitted near to shack door, so you throw it, on exit-entry. Do I remember the Rupert Bear strip on back page of Daily Express showing a row of Jars, a number of which would glow to indicate the strength of the static ?
stay safe.
Cliff.
Gi4CZW Cliff is offline  
Old 5th Jul 2020, 11:09 am   #22
Terry_VK5TM
Nonode
 
Terry_VK5TM's Avatar
 
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,324
Default Re: Static on antennas

Quote:
Originally Posted by crackle View Post
.. I have shown the resistor across the bottom of the balanced feeder where it joins the coax.

So you did, it registered as being up at the other end of the feedline for some reason, must get more sleep
__________________
Terry VK5TM
https://www.vk5tm.com/
Terry_VK5TM is offline  
Old 5th Jul 2020, 2:55 pm   #23
Keith
Heptode
 
Keith's Avatar
 
Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
Posts: 690
Default Re: Static on antennas

The 40W output of the tranceiver corresponds to approx. 63V pk into 50 ohms. As the IRF520 is has a breakdown voltage of 100V, you should be able to find a suitable bi-directional transorb (say 80V) that will deal with lightning induced static pulse but not be activated by the transmitted output.
__________________
Keith Yates - G3XGW
VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm
Keith is offline  
Old 5th Jul 2020, 9:07 pm   #24
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Static on antennas

Hi Keith
Is this the sort of thing https://uk.farnell.com/stmicroelectr...-r6/dp/1689205
I am confused by the different voltages, which one is the important one

Reverse Stand-Off Voltage Vrwm: 68V
Clamping Voltage Vc Max: 121V
Breakdown Voltage Min: 75.6V

Thanks
Mike
crackle is offline  
Old 5th Jul 2020, 11:43 pm   #25
Oldcodger
Nonode
 
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 2,181
Default Re: Static on antennas

Food for thought. Must be some modern equivalent,but the older telecomms members (GPO/po) will remember carbons on the frame to stop lightening strikes. As said- I'd expect modren electronic/digital exchanges needed something more conductive. (GDT?).Would something like this cause problems on RF as low as10/11 m.
Oldcodger is offline  
Old 6th Jul 2020, 9:15 am   #26
Keith
Heptode
 
Keith's Avatar
 
Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
Posts: 690
Default Re: Static on antennas

Hi Mike,
The BZW50-68B might be marginal as it will just start to conduct at 68V (min). The TX might exceed this if loaded into something other than 50 ohms resistive. You'd probably be better off with the 82V part, albeit with slightly less protection.



There's quite a good article on TVS devices at:
https://www.google.com/url?sa=t&rct=...4ijfARBGfrTNS4


Keith
__________________
Keith Yates - G3XGW
VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm
Keith is offline  
Old 7th Jul 2020, 5:30 am   #27
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,803
Default Re: Static on antennas

If thinking of using TVS diodes, look at their capacitance values in the data sheets. It can be a problem on RF signals. Same with ordinary zeners.

MOVs can be lower capacitance, and GDTs lowest of all.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 7th Jul 2020, 9:34 am   #28
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Static on antennas

Thanks
Mike
crackle is offline  
Old 12th Jul 2020, 10:50 am   #29
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Static on antennas

I am planning to install another deeper earth for my antennas in the garden. (8 foot if I can manage to get it that far in)

Has anyone done this and give any tips, I have purchased 2 5/8th rods, a threaded joiner and a nut to drive the first rod in with.

I have also made a 1:1 balun to connect the coax to the dipole feeder. This to me seems the best way to give a DC ground to both halves of the dipole.

I also purchased 2 lightning arresters for the 10m vertical and the dipole.
Does any one have a cut away drawing of one of these, I would be intrigued to know what was inside and how it protects from lightning. Is it in effect just a spark gap from the centre conductor to earth?
Anyway it will be a little extra comfort to have them.

Below is a plan for my new earth termination box that will be about 8m up the garden attached to the fence.
The new deep earth will be bonded to the original 4 foot earth rod I put in by the tree that the 10m vertical pole is strapped to. In the recent hot spell the ground was very dry around that short earth rod and the efficiency of it was rather suspect.

I would welcome any observations on my plan.
Thanks
Mike
Attached Thumbnails
Click image for larger version

Name:	new coax earth box.jpg
Views:	62
Size:	50.6 KB
ID:	210815  
crackle is offline  
Old 12th Jul 2020, 3:42 pm   #30
Guest
Guest
 
Posts: n/a
Default Re: Static on antennas

I wanted to put 7 8' ground rods in my garden and got 14 rods 7 couplers, 7 "top bits" and an SDS drill "hammery bit" (borrowed the drill proper). Rod one went in 4' no trouble, connected second rod and about 6" in it struck chalk then it took 20 minutes of SDSing to get it down. I gave up the 8' malarky and now the other 12 rods are only in 4'. I suppose I must have a fairly good earth.
 
Old 12th Jul 2020, 4:31 pm   #31
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Static on antennas

With a bit of luck I think the Essex clay may be a bit deeper than 4 foot.
I have heard of people using a hammer drill to drive the rods in. But I only have a standard drill with hammer action.

Mike
crackle is offline  
Old 12th Jul 2020, 7:43 pm   #32
russell_w_b
Dekatron
 
russell_w_b's Avatar
 
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
Default Re: Static on antennas

If you're putting radials in they needn't be deep at all. The further out your rods are from each other, the deeper the ground they will penetrate and the better your earth will be. But a bit depends on the topology of what's under there.
__________________
Regds,

Russell W. B.
G4YLI.
russell_w_b is offline  
Old 13th Jul 2020, 7:11 am   #33
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Static on antennas

This project is primarily to take all steps to help eliminate static spikes from entering the shack. It is believed that it is static build up that has already caused one of my rigs to blow its OP mosfets 5 times now.
I believe this is the cause because at the same time, during nearby thunder storms, we have been hearing a clicking sound coming through the TV amp and speakers. It is believed this is static building up on the dipole antenna and arcing across the first tuning capacitor of my T match tuner. The resultant very high voltage discharge to earth is probably travelling around the ring main to the MET at the fuse box. As a result of the recent extremely dry spell and my existing 4 foot earth rods having poor efficiency due to the dry ground.
I am hoping that at 8 foot down the ground will be more conductive.

Mike
crackle is offline  
Old 13th Jul 2020, 9:03 am   #34
PsychMan
Octode
 
PsychMan's Avatar
 
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
Default Re: Static on antennas

I installed an 8 foot ground rod last year. I used rods and couplers etc from Screwfix, probably the same stuff you have. I also have thick clay soil.

I used a combination of 2 different driving methods, which id highly recommend:

- SDS hammer drill (the big type you can break concrete with) - You can get special attachments, but I lashed something up, (sticking a chisel point into an extra coupler I swapped out for a good one for the 2nd rod). I found this got me 70-80% of the way very quickly indeed!

- Sledge Hammer - For some reason the SDS drill stopped being effective towards the end, possibly the amount of rod in the soil served to dampen the vibrations from the drill. But driving the rest of it in with the sledge hammer was pretty easy.

All in all, I think I did it within 30 minutes in total and it was easier than I thought.

I did find the coupling starts to "untwist" as you drive the rods in, I regularly tightened it up, and also did at the end.

Best Regards
Adam
PsychMan is offline  
Old 13th Jul 2020, 9:36 am   #35
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,263
Default Re: Static on antennas

Here's Mr Carlson's video about static on aerials

https://www.youtube.com/watch?v=-_MsOjQEC3k
__________________
Kevin
McMurdo is offline  
Old 13th Jul 2020, 11:43 am   #36
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
Default Re: Static on antennas

Interesting.

Possibly he was right about the spark at the radio being RF related, maybe caused by a flashover to ground somewhere further "up the line" in the aerial system generating damped oscillations a la spark transmitter?
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline  
Old 14th Jul 2020, 12:42 pm   #37
G4YVM David
Heptode
 
G4YVM David's Avatar
 
Join Date: May 2014
Location: Salisbury, Wiltshire, UK.
Posts: 998
Default Re: Static on antennas

Quote:
Originally Posted by G6Tanuki View Post
In times when I've experienced static-buildup-on-antennas I've been happy to fit a low-wattage high-value *wirewound* resistor or two from the static-afflicted parts to the RF ground.

Something like 10KOhms 5 Watts.

The wirewound-ness provides a HF/VHF-choke effect, so it doesn't cause significant waste of RF power or 'RF unbalance' - and a resistor of 10K to the local RF-ground won't cause any significant risk-currents if your DNO's neutral/grounding arrangement fails so the neutral/ground 'floats' towards the supply-phase voltage.
I always thought common wisdom said NOT wirewound resistors.

D
__________________
David, G4YVM.
G4YVM David is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 3:34 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.