[TenTec] In praise of older technology

Wed Mar 5 22:34:23 EST 2014

This is the same reason why a helicopter can be so noisy creating very loud 
"whacking" noise.  As I was told, it is the result of the tips of the blades 
exceeding the speed of sound.

Tony, VE3DWI.
********************

----- Original Message ----- 
From: "Bob McGraw - K4TAX" <RMcGraw at Blomand.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Wednesday, March 05, 2014 8:57 PM
Subject: Re: [TenTec] In praise of older technology

> From an earlier commercial product which I was associated,  we learned 
> that "tip speed" of the fan creates noise.  So less RPM larger and more 
> blades mean lower tip speed for a given amount of air.  Plus sleeve 
> bearing system is quieter than ball bearings although likely the sleeve 
> bearings will need lubrication or fail sooner than ball bearings.
>
> 73
> Bob, K4TAX
>
>
>
> ----- Original Message ----- 
> From: "Rick - DJ0IP / NJ0IP" <Rick at DJ0IP.de>
> To: "'Discussion of Ten-Tec Equipment'" <tentec at contesting.com>
> Sent: Wednesday, March 05, 2014 3:30 PM
> Subject: Re: [TenTec] In praise of older technology
>
>
> Kim, that is interesting about the fan.
> I was unaware of that.
> I have built a few amplifiers, long ago, and always used AC fans.
> I was actually considering a d.c. fan this time around but you just talked
> me out of it.
>
> I have had good experience with the Pabst fans, but they cost about twice 
> as
> much as most other boxer fans.
> I think I'll stick with what I know works.
>
> What kind of material is hardware cloth shield made of?
> I used to put just ordinary screen, like window screen, in front of all of
> my fans.
> Helped keep the garbage out.
> Of course this particular amp has the fan inside and in the middle of the
> box so it won't help in that respect.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Kimberly
> Elmore
> Sent: Wednesday, March 05, 2014 10:17 PM
> To: 'Discussion of Ten-Tec Equipment'
> Subject: Re: [TenTec] In praise of older technology
>
> That makes perfect sense, Rick and I agree completely. It's a fair bit of
> work for, frankly, not a lot of return, even with the 750 W limit. I 
> learned
> a LOT by doing it, so in that regard, I got my money's worth out of it. I
> was intrigued by the Eimac ratings for the tube that say at 4 kV we'll get
> something like 1100 W out of it and so I decided to find out. The sweet 
> spot
> for the amp is 40 m, and that;s where I can get that kind of power out,
> though I have to exceed the 400 mA plate current limit a bit to do it. It 
> is
> most certainly *not* a CCS amp when run that way.
>
> I, too replaced the fan in mine. It originally an AC fan the AC "singing"
> was very apparent and pretty annoying. So, in my infinite wisdom, I chose
> to replace it with a DC fan with a bit more air flow. That fan is much
> quieter. It got even more quiet when I tuned the amp up on 20 m. In fact,
> the fan became silent because the fan stopped. DC fans aren't truly DC: 
> they
> have inverters in them that generate something like 20 kHz AC, and this is
> what runs the brushless motor. Unfortunately, when exposed to that much 
> RF,
> the inverter stops. The fan is certainly quiet, because it's not fanning.
> So, I had to put a hardware cloth shield between the fan and the RF deck.
> The problem went away with that final mod and I learned something new in 
> the
> process.
>
> It's a very fine "one-holer" amp now, and almost certainly one-of-a-kind.
>
> Kim N5OP
>
>
> ________________________________
> From: Rick - DJ0IP / NJ0IP <Rick at DJ0IP.de>
> To: 'Kimberly Elmore' <cw_de_n5op at sbcglobal.net>; 'Discussion of Ten-Tec
> Equipment' <tentec at contesting.com>
> Sent: Wednesday, March 5, 2014 1:41 PM
> Subject: RE: [TenTec] In praise of older technology
>
>
> OK Kim, you convinced me. I won't use that transformer.
>
> I understand why all of that is necessary but it is much too much work for
> the little return of benefit in my case.
> We're only allowed to run 750w here in DL.
>
> The increased HV and lower current would mean better linearity on SSB, but 
> I
> mainly run CW so there is no benefit there either. Was just a spur of the
> moment idea, since I was thinking of replacing the transformer anyway.
>
> The biggest problem as I see it is the lack of space in the RF deck for
> beefing up the coil.
>
> If I am unable to silence the old transformer, I will just replace it with
> the stock Ameritron transformer.
> MFJ lists them for about $150.
>
> The real problem with that amp is its horribly slow T/R relay.
> They need up to 20mS to switch and that means a constant danger of burning
> contacts unless you add some extra delay (which I do). So the relays goes
> for sure. Once the transformer is out, it's simple to service the relay 
> and
> fan.
>
> Thanks for the info. It was very interesting and sounds like you did a
> great job modifying it.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Kimberly
> Elmore
> Sent: Wednesday, March 05, 2014 7:19 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] In praise of older technology
>
> Yes, that's the one. As far as I know, I'm the only guy to ever buy one!
>
> The mod isn't trivial. You'll need to change the filter capacitor stack 
> and
> build a FWB rectifier instead of using the original FW doubler. If you 
> raise
> the B+ you change the plate impedance and so will have to change the 
> output
> tank a by adding some inductance. You'll also have to change the bias on 
> the
> tube. For the output tank, the lower the frequency, the more inductance
> you'll have to add. 160 m is the toughest to tame; I made a powdered iron
> toroid inductor roughly equivalent to the one that's already in there for
> 160 m and placed it under the stock large air-dux inductor. It has very 
> high
> RF voltages on it and so will need some serious insulation between it and
> the bottom the case. I used about 1/4" rubber sheet. You'll then need to
> move the taps for all the bands up through through 20 m. I did this by
> experimentation so that I had the load and tuning controls where I wanted
> them (they no longer strictly match the guide on the front panel). You'll
> also have to be very careful tuning it because the RF voltages are much
> higher, now. It must never be run lightly loaded as you are certain to 
> flash
> over the band switch. Once I figured it out and put stick-on markers for
> tune and load pointers, it was easy
>
> I upped the bias on the tube based on the Eimac spec sheet. Failure to do 
> so
> will cause the tube to dissipate more than 500 W in an idle condition. 
> I've
> forgotten what the new Zener value had to be, but it was a stock value and
> the idle bias is set to be (I think, it's been a while) about 60 mA. The
> primary requires 240 VAC -- you'll no longer be able to run it on 120 VAC.
>
> Kim N5OP
>
>
> ________________________________
> From: R. Eric Sluder-W9WLW <resluder at yahoo.com>
> To: "cw_de_n5op at sbcglobal.net" <cw_de_n5op at sbcglobal.net>;
> "tentec at contesting.com" <tentec at contesting.com>; "tentec at contesting.com"
> <tentec at contesting.com>
> Sent: Wednesday, March 5, 2014 11:35 AM
> Subject: Re: [TenTec] In praise of older technology
>
>
> That explains the upgraded Peter Dahl transformer you can still buy for 
> the
> AL-80a. I've considered swapping my transformer out because it looks a
> little weary for its age and such. I fear a short could be in its windings
> in the not to distant future. My amp I believe came from a moist
> environment, and that is why I have the concern over a short. The outer
> paper layers don't look their best.<br/><br/>Eric<br/>W9WLW<a
> href="https://overview.mail.yahoo.com?.src=iOS"><br/><br/>Sent from Yahoo
> Mail for iPad</a>
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
>
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec 