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Latest Topics

Topic Created Posts Views Last Activity
Anyone have a link for a build it yourself car battery charger? Apr 21st 2021, 17:31 2 7,282 on 22/4/21
NMO 2 / 440 on plastic roof. Ground plane ?? Apr 8th 2021, 15:26 2 5,275 on 29/6/21
Is it true that high SWR reflections don't fry finals? Feb 22nd 2021, 06:59 5 5,056 on 22/2/21
WIRES Node getting into my packet station Feb 1st 2021, 21:42 7 7,304 on 20/2/21
Design for 5/8 wave on 10 meters. Oct 20th 2020, 11:02 2 5,709 on 20/10/20
Why won't my ARRL designed vertical tune on 20? Aug 1st 2020, 06:47 7 5,358 on 8/8/20
Vertical antenna using a wire as a radiator. What gauge? Jul 23rd 2020, 08:17 3 5,362 on 24/7/20
Interesting Voices Discussion Net - DMR TAC316, Wed 10/2/2019. Sep 28th 2019, 05:02 2 6,404 on 2/10/19
DMR Discussion Net. 5/15/2019. May 6th 2019, 06:53 4 8,119 on 16/9/20
Windom antenna. How to design the choke. Feb 14th 2019, 15:40 2 8,090 on 14/2/19

Latest Posts

Topic Author Posted On
Anyone have a link for a build it yourself car battery charger? N1AUP on 21/4/21
I need to buy a 2 amp, battery charger / maintainer to keep the batteries in my tractor fully charged if the equipment sits.

I know there are a ton of commercial chargers on Amazon, but everyone is complaining about them. I'd like to build a heavy duty, high tech, 12 volt battery charger / maintainer that I can attach to the battery bank on this tractor (two type 31s), and let it go.

Does anyone have a link to a kit, or a set of plans to build something first class?

NMO 2 / 440 on plastic roof. Ground plane ?? N1AUP on 8/4/21
I plan to mount a 2 / 440 FM radio in a backhoe that I just bought.

A plastic roof sits on top of a steel ROPS cage that forms the sides and top of the cab.

If I mount a 5/8 wave antenna on top, it's going to need a ground plane.

1. Is the ROPS cage enough of a ground plane for the antenna if the 3 inch square steel bars makes a rectangle about 2 x 3 feet with the antenna on the plastic in the middle?

2. How close does the ground plane have to be? Could I mount the NMO on an L shaped bracket, and assume that the backhoe arm and frame of the tractor, four feet below, is enough ground plane?

Or should I get a deep NMO, mount it in the center of the plastic roof, and put some sort of a hardware cloth mesh screen under the plastic roof?

Finally, do I need hardware cloth, or can I use 4, 19 inch pieces of wire to act as ground radials like with a 5/8 base antenna?

Is it true that high SWR reflections don't fry finals? N1AUP on 22/2/21
I was always taught that SWR mismatches blow up finals because too much RF is reflected back at the transistors. The quote from a ham's web site seems to say that this is not correct.

So I'm still not sure. Which is correct?

I am reading those two articles.
Is it true that high SWR reflections don't fry finals? N1AUP on 22/2/21
Is this true?

"So, why do people think they can blow up their rigs or linear amplifiers when there is a high SWR on the antenna?

Because that can happen, but it is not due to the reflected power!
There is a totally different reason.
A high SWR on an antenna probably means that the antenna is not tuned to the frequency that is being used. This, in turn, means that the antenna has some inductive or capacitive reactance that is de-tuning the final amplifier. De-tuned final amplifiers draw far too much current and can burn up. The rig or linear amplifier will have to be re-tuned to avoid creating too much heat.
Many linears and nearly all tube amplifiers have some tuning knobs that allow you to "dip the plate current" or adjust the SWR by adjusting something on the front of the device.
Transistor rigs usually do not have any tuning adjustments. To avoid the extra heat created when running a de-tuned amplifier, there is a protection circuit that will significantly reduce the output power if the SWR is high. "

WIRES Node getting into my packet station N1AUP on 20/2/21
Thanks. Thinking....

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