[RFI] SO2R 2nd Harmonic Interference
Grant Saviers
grants2 at pacbell.net
Sat Sep 29 18:22:01 EDT 2018
I have found the "Battery Minder" products quiet and reliable. Not to be
confused with Battery Tender which have had a high failure rate for me.
The Minder brand uses a pulse charge float technology and has recovered
partially sulfated batteries for me and has the lowest water loss of any
float charger I have used.
Two are on 24x7 24v 2 to 4a outside (48v x 220AH), one 12v 1a outside on
24x7 (12v x100AH), and one inside 12v 2a on 24x7 (12v x 220AH). I
haven't added chokes on any of them.
Not cheap but worth it as batteries really last and are always ready to go.
Grant KZ1W
On 9/29/2018 13:52 PM, Randall K Martin wrote:
> I have been trying to solve an interference problem for quite a while
> here at my QTH. Symptom is that when I transmit on 40M CW, even at QRP
> power levels using bandpass filters and transmitting stubs, the second
> harmonic on 20M is a wide signal, covering 30-40 KHz. As per advice
> given by Frank W3LPL regarding RF flooding, I started searching for an
> electrical device (probably charger/wall wart).
>
> I eliminated my own home as the source by testing with battery power
> and all circuit breakers turned off. Through more testing, I found
> that even at 100 milliwatt output on 40M, I still got the 20M wide
> band hash, but only when I pointed my 40M antenna at my neighbors house.
>
> Today, I got together with the neighbor and he let me snoop around
> with a portable Rx. Voila! Culprit is a cheap little trickle charger.
>
> DBT Auto Electrical Products PTE LTD Part no. 021-0123
> "Household automotive battery charger" 120V input and 12V output at
> 750 mA
>
> Question: Is there a battery charger that any of you can recommend? I
> tried wrapping the 12V leads of the current charger roughly 10 x
> through a large toroid and there was little if any reduction in
> interference.
>
> 73 Randy K0EU
>
>
>
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