Caterpillar discover the noise from the tips of blades the expensive way. The
fan blades on their V12 diesel engine that came with our 1 Megawatt generators
at work broke the sound barrier and talk about noise!!! They had to retro all
their engines with that particular fan set. Its the same engine used in their
D9 bulldozer too.
Eric
W9WLW
On March 5, 2014 10:34:23 PM EST, Tony Lelieveld <va3dwi@gmail.com> wrote:
|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@Blomand.net>
|To: "Discussion of Ten-Tec Equipment" <tentec@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@DJ0IP.de>
|> To: "'Discussion of Ten-Tec Equipment'" <tentec@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@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@DJ0IP.de>
|> To: 'Kimberly Elmore' <cw_de_n5op@sbcglobal.net>; 'Discussion of
|Ten-Tec
|> Equipment' <tentec@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@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@yahoo.com>
|> To: "cw_de_n5op@sbcglobal.net" <cw_de_n5op@sbcglobal.net>;
|> "tentec@contesting.com" <tentec@contesting.com>;
|"tentec@contesting.com"
|> <tentec@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>
|> _______________________________________________
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