[Lf] Re: [Lowfer] Re: Amplifiers for 136k

[BOB RIESE]

HI Dave

the Frank Notes state a simple input pot to adjust level and
a proper 8 to ( ? ) antenna transformer should be all that is needed
couple of years ago I plugged the part number in to the net and quickly
found all the device info. can be set up for dual or single voltage
supply
and it will need a big heat sink as it will be running full power at a
high
duty cycle.

I cross posted this to the AMRAD reflector 

you may want to check at www.amrad.org . I havent been on the site fer a
while
so I dont know if this is covered or not

as I havent started to build anything I would like any info pertinent to
this as well
other than shielding the input/output and making a multi tapped
transformer for 
output it should work . 

Bob


On Fri, 30 Aug 2002 09:01:15 +1200 "Dave Brown" <tractorb at ihug.co.nz>
writes:
>Hi Bob
> Any way to get more details on this from Frank?
> I have been thinking of trying the LM1875 and one or two other 
>similar amps
>for this purpose so very interested to hear Frank has already done 
>it!
> 73
> Dave
>ZL3FJ
>----- Original Message -----
>From: "BOB RIESE" <riese-k3djc at juno.com>
>To: <lowfer at mailman.qth.net>
>Sent: Monday, August 26, 2002 4:21 AM
>Subject: Re: [Lowfer] Re: Amplifiers for 136k
>
>
>>
>> Hi All
>>
>> I just pulled out the info on the National Semiconductor LM 1875
>> this is a 20 to 30 watt audio chip that Frank Gentges tested to
>> , I believe 300 Khz. With a good heat sink this device should 
>produce
>> 25 watts out at 136 Khz. It is a simple idea to get some usable 
>power
>> and the chip, when I looked into it, was 3 bux or so. All you should 
>need
>> is
>> a transformer to get you from 8 ohms to the antenna imp. All fits in 
>a TO
>> 220
>> package and needs 5 resistors and 7 caps to get it operational
>>
>> Unfortunately I only looked into it and never bought any but that 
>should
>> be
>> a winter project.
>>
>> this would make a transmitter with the power of the average small 
>airport
>> NDB
>>
>> Bob  K3DJC
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>