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Monday, 14 May 2018

Power supplies for radios, a cheaper alternative?

I have been for a while looking to replace the existing shack power supply arrangements with something that utilises Anderson Powerpole connectors, and can distribute that power from one supply, a suitable supply from a radio equipment supplier would at least come to just shy of £80-£100, but there may be a cheaper option.

YouTube user "fredintheshed" purchased a cheap 40A PSU from eBay that could do the job and he used it to run the CRT 6900N (which in actuality is the AnyTone AT5555 with blue readouts) with very little problems, apart from one obvious one, safety, because this type of PSU has exposed screw terminals for mains in and 12-volt out.

This supply can output at 13.8v DC with no real problem, it simply requires an adjustment of a potentiometer next to the terminals preferably while a voltmeter is in circuit, though most CB and Amateur equipment will take 14 volts happily as car alternators usually output here.

The cost, less than £20 shipped, however to get this thing working you really need to follow electrical safety rules, connect this unit to earth (that is power it with 3-core cable), a fuse inline on the live side would not hurt either, ensure the exposed live terminals are covered or the whole unit is enclosed so it cannot be touched, and use cable rated for or even above what you expect to draw to reduce fire hazard, the wire gauge rule also applies for the DC out.

Another little tip is to fit an ammeter to the DC output so you can be aware of how much current you are drawing, a linear amplifier (if you're duly licensed and it does not exceed your allowed power output) could potentially pull a lot of current, as could a radio alone depending on it's TX output power, a CB on the other hand, due to the fact it wouldn't exceed 4 watts ERP (and 12 watts PEP on SSB) would pull such a small amount of current it wouldn't put a lot of load on the supply, a voltmeter would also be handy to make sure the voltage output is stable.

Fred's video on YouTube also showed the units to be RF clean (at least on 27MHz as from what I can tell he is not licensed) which surprises me considering most Chinese imports tend to generate more RF pollution than they ought to (the only thing worse is PLT units), though this test was done by disconnecting the antenna from the radio.

Should you buy one of these? Ideally only if you're competent at electrical wiring (though if in doubt always seek the advice of an electrician), I plan to get one of these myself and see if it powers my CRT SS9900 better than the computer PSU I am forced to use for it.

Finally if you do buy one of these, be aware there is a cooling fan on top of the unit, if you enclose the unit it is vital that you do not obstruct the airflow to the fan for obvious reasons.

All in all these supplies seem good value for money, so I think for me that is worth an investigation.

73 de 2E0EIJ

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