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Equipment discussions, questions, answers.  Focus in on QRP and backcountry operation, but anything equipment related goes.


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ZL1THH posted in Equipment on 2020-12-29 10:33

For anyone interested, I broke down the 817 and weighed it all, looking for savings to make it light enough to take on a long trip.  Hoping to get it to ~700g with batteries.

- Covers are 300g: replace with carbon
- Energizer Li AA's lightest choice that I can get in time.
- Microphone is 170g
- misc parts: speaker bracket, spkr, so-239
- lighten chassis


ZL1THH posted in Equipment on 2020-12-09 15:52

You just put a high value R across the line for static. Just has to have breakdown voltage greater than max for your transmitter at VSWR=N

You don't use a spark gap to discharge static, as it is making RX noise.

ZL4NVW updated in Equipment on 2020-12-06 16:40

I've just fitted an inductive 133uH discharge coil from feedline core to ground at the base of the mast for my 80m dipole - 100 turns of antenna wire on a length of 40mm plastic pipe. Which will hopefully work to discharge static from the non-grounded half of the dipole without passing RF (comments on the value welcome, just went off a comment that '100 turns on a beer can should be enough (then remove the can)') .  Unfortunately my antenna <1.5:1 SWR band seems to have dropped from 140kHz to 100kHz either side of centre - though at the low point is still 1:1 at the usual tuned centre freq of 3.650. Not sure if that's the result of the coil, or due to something else, but is annoying.  Solves the static, but not the lightning risk.  Will build another for the (40m/15m)-20m-17m fan dipole.

Separate conversations here (https://forums.qrz.com/index.php?threads/lightning-static-buildup-protection-for-efhw-on-house-gable.737891/) have convinced me that the EFHW coax run needs re-routing down to ground outside the house rather than through the loft-space so that it can get effectively grounded at the choke.  As I should have realised the UNUN (matching transformer) on the EFHW provides a low-resistance DC path between core and shield so the discharge device connected to the feedline core is not required for an EFHW so long as the shield is grounded at the choke.

All of which is about static buildup, and none of which deals with lightning strike. The spark plug sounds like a good cheap option.   I was getting a good 15mm spark gap between centre-pin and casing yesterday. The gas-discharge lightning protection devices cost more each than my Kenwood cost me by the time they're converted to NS$ and landed in NZ.
 

ZL2OZ posted in Equipment on 2020-12-06 11:17

 We don't get lightning often here in Dannevegas, but it can be a doozy when it arrives. I too just remove the antenna from equipment. but would like to install some form of lightning protection. I don't like seeing sparks jumping from the antenna plug to any metal object within 10 to 15mm! A bit scary! Oh, and painful if your handling it at the time of a strike!! Suggestions? (Apart from 'Don't handle it!'

ZL1LC posted in Equipment on 2020-12-06 09:31

You don't have to be in a thunderstorm to have a shocking experience with an antenna.  


When I was an apprentice in a desolate place called Waiouru, we had a dipole strung up outside the workshop.  It had the braid of the coax grounded and tapped onto the center wire of the coax was a spark plug with a 0.030" inch gap.  (No metrics for me, so I'll let someone figure it out.)  In the winter, when the snow clouds were down low, that spark plug was zapping away all day as it discharged the static electricity that had built up on the antenna.


We don't normally get the huge lightning strikes that they get in the USA, because our humidity is higher, so I suggest as a good starting point, you need to start reading some of the ARRL handbooks.  Having a high wattage 100k ohm bleed resistor across the antenna to ground is a good start, but you need a fast DC (low resistance ) path to ground if there's any close lightning.  


The best solution is not to have your radio connected to the antenna during a thunderstorm.  That keeps the expensive item safe.  Fixing an antenna or coax is a lot cheaper and simpler.


73

Jim  ZL1LC

ZL4NVW updated in Equipment on 2020-12-06 09:31

Not specifically QRP related but ... 

Last night in a particularly heave rainstorm I was sitting at the computer listening to what sounded like an arc-ing electric fence inside of my antenna switch. 

Disconnecting the antenna cable proved to me quite emphatically (shockingly, even) that this was electric discharge happening from the core or the coax / connector coming from the antenna to the case & thus earth.

Dipoles:

The shield of the feedline is grounded at both mast and shack - but the core obviously not.  I had been disconnecting at the mast when away and when lightning was forecast - but clearly that's not good enough. 

  • Putting static discharge coils between mast-ground and the cores of the 2 dipole feedlines is a no-brainer.  
  • These presumably really should have some arc-gap or similar lightening protection too ...

End-fed half wave:

  • Feedline shield is grounded at the shack only (there is no mast) 
  • Feedline core is not currently protected at all
  • The unun is on the house gable with no ready access to ground and whilst I can run a static discharge ground cable down the outside of the house, I suspect that running something sufficient to ground a lightning strike is less simple and aesthetically acceptable

So 2 questions:
1) What would you you do to safely discharge & protect an EFHW?  
2) What arc-gap or similar lightening protection devices do you use and is any of it available in NZ?


Matt

ZL2BH posted in Equipment on 2020-10-20 06:21

Jim, What a cool device you have made and thanks for the tips re the wire etc
John
ZL2BH
I inquired to the guys at QRPver to see if their single-band QRPver1.3 radio can be extended out to receive the mountain radio service frequencies.  The default radio covers only the the 80m amateur band on both tx and rx - but for my backcountry use the ability to receive the nightly mountain and long-range weather forecast on 3.261 / 3.345 USB is a necessity.

The response was that yes - this can be done so long as you let them know before you order.  I hope the info is of use to someone.

Note that I did not inquire about transmission on the mountain radio service frequencies.

Email trail is below


Matt - ZL4NVW

===



Hi dear Matt
Yes, it can be done during the manufacture of the device. You just need
to contact us before ordering.

Regards, _____

73!

21.07.2020 23:41, Matt Briggs - ZL4NVW пишет:
> Hi,
>
> I'm interested in your 80m qrpver1.3 which seems to work very well on 80m.
>
> However in addition to the 80m amateur band, I also need to be able to receive the 'mountain radio service' weather forecast broadcasts on 3.261MHz and 3.345 MHz, USB.  Is it possible to open up the receive on the 80m radio to receive these?
>
> If you are able to do this, I am sure that you will receive many more orders from New Zealand - as being able to receive weather forecasts is a requirement for most field users.
>
> Regards,
>
> Matt Briggs
>

ZL1LC updated in Equipment on 2020-10-05 14:48

I can 3D print Wire Winders which are ideal for lightweight QRP portable operation.  I have attached a photos of the type that I recommend.  The standard size is 250mm overall but I can make them smaller if required.  The 250mm version weighs approx 30g.  
The best wire to use is the really thin stuff, ( #534) from thewireman.com    He is used to posting to NZ.
Steal a bit of knicker elastic to hold the wire on and you are away.

https://www.youtube.com/watch?v=o8RoYrmr8o8 shows them (about the 8 minute mark,) and a 1:1 balun, which can also be made. 

These are printed in PLA which is fine for portable operation, but probably won't last forever if used in a permanent role.  Some things that I have printed and left outside are still looking great more than a year down the track.  Any random colour except brown or green, so that you can find them at a field deployment site.

Provided you wind on your wire in a figure 8 pattern, the great thing with these winders is that when you come to deploy the wire, you simply secure the loose end to the balun/unun or dipole centre piece, hold the winder through the round hole, and walk away letting the wire wobble off cleanly.

The biggest cost is the postage, which is $6 for an NZ Post bag.  I can get six winders in the bag easily.  These winders are priced at NZ$2.50 each which is basically covering costs.

Also, if you find something else on thingiverse.com that you'd like printed, email me. 

My email is jimreednz@gmail.com

Img 1085 original original

ZL2TUD AKA ZL2XRF posted in Equipment on 2020-06-18 20:41

here in nz it depends on what you require there are many options some of the most expensive are Spectra braid and Vectran braid these have no stretch and a very small cord will be rated somewhere near a ton breaking strain
however uv stabilised polyester offers a very cheap long lasting (usually white with a blue fleck in it). Donaghys use to make rope here but now seem to be in Aus
any yacht chandellry will have a good range. Cookes wire services also carry some ropes

ZL4NVW posted in Equipment on 2020-06-01 09:51

Does anyone know an NZ source for black antenna support rope (2.5 - 4mm, UV stable, dacron or equivalent)?  Maybe dacron is called something else in NZ, but I can't find anyone in NZ selling it.

ZL2TUD posted in Equipment on 2020-06-29 13:11

I bought some of this stuff last week to use as draw cords through a120m length of conduit
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