[TenTec] Switched audio filters

[Tim]

Hi Rick,

Our paths have been similar except that I switched from the technical 
side of radio to the technical side of TV in 1998. I think the last time 
I worked at the chip level was for an automation system for a radio 
station in the mid 80s. I found the 7407. It would let me use a logic 
gate to switch +28 volts with out having to use a relay. Saved the 
station $100 each time I used one since I didn't have to buy the part 
from the automation company.

I copied the 208 filter as well, even etched the pc board. I wired it 
for the 515 and gave it to my Dad for Christmas one year. I have that 
filter, but I know the chip isn't made anymore. I would guess that an 
ordinary audio op amp would work. So yeah we can see what someone else 
might suggest.

By the way, apparently I bought an Idiom Press Scaf-1 several years ago. 
I have the receipt which I have sent to them, but never received the 
filter. One review I read though suggested that the NE QRP 
<http://newenglandqrp.org/store> club's filter was much better and half 
the price. It's very close to the original price for the 208. 60 Hz is 
much better than 450 Hz so the NEScaf may be a nice thing to add to an 
old QRP rig.


Tim
KE4KE


On 03/23/2016 11:19 AM, rick at dj0ip.de wrote:
> Hi Tim,
>
> I honestly can't say.  I might be able to find out.
> We're talking 1970s here.
> I built several and at least one was exactly the 208 circuit.
> I think I still have some ICs from that era but I'm not sure.
>
> I basically stopped building things about 1983 when changing jobs from
> technical to sales and moving to a small city apartment with no place for a
> workshop.
> The only thing I've built since then is several antenna matchboxes, and
> about 100 antennas!
> Oh and also about 100 baluns.
>
> I could not specify an IC today.  I would have to do some research and see
> what people are using.
> I'm sure someone else here has a suggestion.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt, Germany)
>
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Tim
> Sent: Wednesday, March 23, 2016 4:11 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Scout for Sota
>
> Hi Rick,
>
> When building a filter what chip did you use or would you use now? The chip
> used in the 208 was discontinued years ago and I haven't done any real
> building since, well about that long ago...
>
> Thanks,
>
>
> Tim
> KE4KE
>