Question about Battery Eliminators on TwoWay Radios

[raphaelriv]

why would one battery eliminator cause noise on one two way radio and not another?

 

[RODALCO]

Battery eliminator

What type ??

Switchmode or series regulated ?

 

[raphaelriv]

re:

switch mode

 

[Hero999]

There you go then.

Switch mode power supplies are noisy so it's hardly suprising.

 

[Sceadwian]

One might be meant to be run from a switcher and able to regulate the higher frequency ripple. But a common wall wart only usually has 120hz ripple, high frequencies might not even be considered in the design and might pass through.

 

[stevez]

"Battery eliminator" sounds like an AC sourced power supply that is powering something made for batteries. It's likely that any AC supply will present more noise to the power input than a battery. Note that power leads can be effective antennas.

One radio may simply be more sensitive, by chance. One radio might have been designed with an external source in mind - the other may have been designed with a relatively noise free power input in mind.

The current draw of one radio might be profoundly different from the other - that affects the noise/ripple from the power supply.

 

[Hero999]

It also depends on whether the suply is regulated or not. Linear supplies are practically ripple free, unlike a simple transformer, rectifier and filter capacitor.

 

[Sceadwian]

I doubt it's a wallwart vs a regulated wallwart. Because honestly I've never taken apart a wall wart that had a linear regulator in it, though that particular brand and or model of radio might require one. Even a bad radio design should be able to deal with moderate 120hz ripple from a full wave wall wart rectifier especially with even half assed filter capactors. A lot of them might have problems with say a 10khz switching frequency on a slim line adapater. High value electrolytics can't filter out high frequency noise's from a switcher, if the radio even has any buffer caps (might depend on the power supply)

 

[stevez]

I tried to run my well designed handheld transceiver on a supply with moderate ripple and the hum as reported by receiving stations was significant. A friend who repairs/modifies equipment like this noted that many handheld units do not have the on-board filtration/regulation. There is no audible hum now that I have it on a supply with 5 to 10 mv ripple.

 

[Sceadwian]

The filter caps to heavily filter out the humm are pretty large, not surprising on a hand held unit.

 

[stevez]

My pal who is in the business told me that many of the radios he works on run at something like 8 volts dc - all incoming DC is run thru a regulator/conditioner. In some cases, he tells me, there's a dc to dc convertor. In either case it allows for some significant noise reduction. Apparently that is what is absent on a handheld.

Worth mentioning is that a voltage regulator can and does reduce ripple. The spec sheet for an LM317, LM7812 and similar will show 60 db or more capability. That eases the need for super large capacitors.

 

[johnsmith123]

battery eliminators

why would one battery eliminator cause noise on one two way radio and not another?

I had/have the same problem. No noise when run on batteries. Check this link out:

https://www.electro-tech-online.com/threads/noise-free-6v-dc-power-supply.23946/

hope this gives you some ideas/help.