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Author Topic: In the dumb questions department . . .  (Read 736 times)
KD5MAW
Member

Posts: 75




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« on: January 08, 2001, 11:36:19 AM »

Anyone have any idea why tx output on an ht would appear to decrease when operating with it hooked up to the plug-in charger? Let me explain: until I can get the radio I want for a VHF/UHF base station, I'm running an Icom W32A hooked up to a roof-mounted folded unipole ground plane antenna. Had serious intermod problems running the external antenna, so I put a bandpass filter on the feedline; bingo, noise gone. Anyway, I have no problem waking up one distant repeater (~60 miles) on the battery pack, but get no response when running on the charger. Seems like the situation would be just the opposite.
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N2MG
Administrator

Posts: 122



« Reply #1 on: January 08, 2001, 12:07:01 PM »

Is the charger designed for this application or is it one that just seems to work?  IOW, is it the radio's original charger made by the manufacturer or something you picked up at Radio Shack?  I suspect that the specifications may not be be sufficient (voltage, current).

You might need to take some measurements (as my old engineering mentor used to say, "Gimme data, man, data")

1. Verify the charger is spec'd to deliver what the radio needs (TX requires WAY more juice than RX).
2. Verify the charger is actually working as spec'd.  (You need a voltmeter).
3. Verify the RF output of the radio is OK (need a RF wattmeter)
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AA9HD
Member

Posts: 10




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« Reply #2 on: January 08, 2001, 12:11:53 PM »

a battery charger is usually of a low amperage, much lower than the radio requires. for example, most ht's require 2A or so to drive them to their highest output level.  A lot of chargers only supply 300 to 500 ma of output.  when you are charging a battery while using the rig, you are "floating the battery" between the charger and the rig.  since the battery is pretty dead, the charger has to try to supply the rig with the higher amount of power needed to transmit.  it can't, and you end up with no signal and a potentially fried charger.  i would go and buy a little 5a supply (radio shack sells them) and use that.  as a side benefit, many rigs will charge the battery while it's plugged in as well.  it's definitely the way to go for home use of an HT.

73!

Chris, aa9hd
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WB6BYU
Member

Posts: 13040




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« Reply #3 on: January 08, 2001, 12:37:07 PM »

In addition to what the others have mentioned, some HT's will
disconnect the power to the radio when the charger is attached.
This is because most chargers are not well filtered, and using it
on transmit results in a messy signal.

But I suspect that the others are correct:  when external power is
applied, the batteries are disconnected.  And the charger alone
can't supply enough current for the transmitter.
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Guest

« Reply #4 on: January 08, 2001, 01:06:50 PM »

Ditto on the above.  Haven't used the radio you have, but can tell you that I keep a Z1A for emergencies.  The owners manual specifically warns against using the radio with the battery charger attached.  It was not intended to be used a power source and will damage it.  It is very possible your ICOM is the same.  
73
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KD5MAW
Member

Posts: 75




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« Reply #5 on: January 08, 2001, 01:29:38 PM »

OK, this is making sense, particularly if the charger (which was furnished by Icom) plug cuts the battery pack out of the equation. My original post was based on the assumption that the transmitter would draw current from the pack, not the charger. Could be a bad assumption - need to look at the schematic and see if I can tell what happens there. I have been running the radio this way with a fairly fresh pack installed, but if the pack goes by-by when the radio is hooked up to the charger it would seem likely that tx current requirement would grossly exceed the charger output. Which can't be much, since it's a slow-as-molasses trickle charger. Worse, this is an "unregulated power supply" situation. Another clue: I've received "scratchy" signal reports when operating with the charger, but not when running from the pack. I think y'all have this one nailed. Thanks for the help.
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KE6BGH
Member

Posts: 33


WWW

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« Reply #6 on: January 08, 2001, 06:20:09 PM »

1. Have you checked for AC ripple riding onthe DC when using your wall charger?  With just a dc voltage measurement things may seem fine, but if you have a volt or two of AC riding on the DC it can do interesting things to the circuitry performance.  Since you say it is a CHARGER, sre you sure it works as an operating power supply?

2. When you connect to the tranmission line with a battery, you are isolated from your domestic power system.  Plugged into the wall you are no longer isolated, and if your antenna is grounded properly you may be getting ground loops that that can also do interesting things.

Note that interesting does not mean good most of the time.  Like the old curse--"May you live in interesting times".

Hope this helps!

Dave KE6BGH
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K0CBA
Member

Posts: 295




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« Reply #7 on: January 08, 2001, 09:09:36 PM »

There are battery "chargers" and battery "eliminaters".
They are not necessarily interchangable.
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KD5MAW
Member

Posts: 75




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« Reply #8 on: January 08, 2001, 10:22:42 PM »

The W32A pulls 1.6A on tx, high power (5w). The charger is just that, a charger. Output = 200mA. Considering that I'm using the radio as NOT designed, it's working great with the roof-mounted unipole since I quit using the charger. Fortunately, I've also got a fast charger and several batteries. Mickey Mouse setup, but it'll do until I get a real radio. Thanks again.
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