Hi,
Sorry if this has been addressed, but I have a question regarding the grounds on this board. Are the grounds for the Raduino (terminal 4) and the audio grounds considered common grounds? And can they all be tied together to a metal chassis? I believe I have read of people isolating the mike & speaker jacks from a metal chassis, but I'm not sure why this would be necessary The schematic shows the keyer jack grounded to chassis, but not the mike or speaker jacks. Is the lack of a ground symbol saying the mike & speaker shield terminals should be isolated? Thanks for the clarification!? Bill A.

I assume a 10M leaded resistor from RF-in to ground is what you are
suggesting?

That will be a lot simpler for me to do than adding an RF gain control.
The front panel is getting pretty crowded!

tim ab0wr

On Fri, 20 Apr 2018 15:07:47 -0700
"Don, ND6T via Groups.Io" <nd6t_6@...> wrote:

The principle idea of my AGC mod is built around the potentiometer RF
gain control. It is meant to work in concert with it. As such, that
potentiometer works as a static dissipation device to ground. My
antennas here are both end-fed random wires (one 175 feet long, the
far end up 100 feet) and are excellent static accumulators unless
provided a path to ground. A 10 Megohm resistor will do that, by the
way. I cannot overemphasize the desirability of a manual RF gain
control, even with an AGC. I think most operators, even with the
fanciest of rigs, use that control extensively. Best noise reduction
device ever! 73, Don

My braid is grounded at the entrance box to the house. I also made up
shorting plugs for when I unhook the antenna so the center conductor
and braid should both be at the same potential.

tim ab0wr

On Fri, 20 Apr 2018 16:55:25 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

The AGC writeup does mention that the RF gain control is assumed,
but the diagram just says "To K3 pin 14" where I assume it should say
"To Wiper of RF Gain Pot"
Better yet, include the pot in the drawing.
Perhaps it should also mention the need for static discharge.
Regardless, by all accounts, that's looking like a simple and
effective AGC implementation.

We get lots of thunderstorms blowing through, and I generally just
try to unplug antennas when I see them coming.? I believe I recall
reading once that simply using coax offers adequate protection if you
give the braid a good earth ground.? Not sure how bulletproof that
is, but my braid does have a good earth ground.?

On p48 of July 2002 QST, it recommends something like this device:
? ??
which costs more than a Bitx40.? Is there a cheaper alternative?

Gas discharge tubes (GDT's) are often used for lightning protection
on phone lines. Seem to be available with capacitances down to? 5pf,
so should work at RF.
Might well
be what's in that device above. Perhaps there's also a fuse of some
sort between the antenna wire and the GDT?

Back 50 years ago, they recommended building a spark gap for use as a
lightning arrestor, the older hams who wrote about it probably had
fond memories of spark gaps. Basically a homemade GDT, using locally
available air instead of some exotic gas.

Anybody know what works?
Protection schemes for this sort of thing are inherently dangerous as
they are generally untested and might give a false sense of
security.? Consequences can be considerable. Unplugging antennas is
still a good idea, will still have a rig if the house doesn't burn
down.

Jerry, KE7ER

On Fri, Apr 20, 2018 at 03:07 pm, Don, ND6T wrote:

The principle idea of my AGC mod is built around the potentiometer
RF gain control. It is meant to work in concert with it. As such,
that potentiometer works as a static dissipation device to ground.
My antennas here are both end-fed random wires (one 175 feet long,
the far end up 100 feet) and are excellent static accumulators
unless provided a path to ground. A 10 Megohm resistor will do
that, by the way. I cannot overemphasize the desirability of a
manual RF gain control, even with an AGC. I think most operators,
even with the fanciest of rigs, use that control extensively. Best
noise reduction device ever! 73, Don

I guess that then assumes you have a very simple tuner (Cap-L leg)? No impedance transformers, inductors to ground, etc.


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
Like us on Facebook!

Moderator – North American QRO Group at Groups.IO.

email: bill@...

I agree! But if the problem here is static buildup then a tuner won't
help any more than the coax connector on the rig!

tim ab0wr

On Fri, 20 Apr 2018 17:37:45 -0500
"K9HZ" <bill@...> wrote:

That is not where you want static charges dissipating! Chokes to
ground, resistors, at the antenna. All a better place for it (the
fire) to happen.


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
PJ2/K9HZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
Like us on Facebook!

Moderator – North American QRO Group at Groups.IO.

email: bill@...



-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Tim
Gorman Sent: Friday, April 20, 2018 4:05 PM
To: [email protected]
Subject: Re: [BITX20] receiver overload

I'm sure it happens. But not consistently. You need wind and
something to create the charge like blowing dust. If the tuner is
dissipating the charge why doesn't the rig itself do it, at least
with an unbalanced feed?

tim ab0wr

On Fri, 20 Apr 2018 08:47:00 -0500
"K9HZ" <bill@...> wrote:

Unless the antenna is picking up a static charge and the antenna
tuner is acting like an impedance to ground draining that charge
off. Don't laugh, it happens.


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
PJ2/K9HZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
Like us on Facebook!

Moderator – North American QRO Group at Groups.IO.

email: bill@...



-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Tim
Gorman Sent: Friday, April 20, 2018 8:42 AM
To: [email protected]
Subject: Re: [BITX20] receiver overload

Usually a tuner will increase noise, at least atmospheric noise, as
the tuner creates a match between the receiver and the antenna. A
matched antenna shouldn't "tame" the noise. If that is actually
happening then a closer look at the system might be appropriate.

tim ab0wr



On Fri, 20 Apr 2018 11:39:39 +1000
"John Sharpe" <johsharpe@...> wrote:

Hi all,

I just had a thought about new users of the uBitx and the Bitx40.

I have both of these fine rigs but with my good antenna - a
ZS6BKW
<> at 30
feet
- the receivers are swamped by noise and big signals on 40 metres.

When I tested just now a 59+ 10 signal on my IC-7300 was
unreadable on the Bitexes with the big antenna (which has a low
SWR at 40 metres) because of noise. With an antenna of just 6
feet of wire in the shack the signal was readable (but weak) on
the Bitexes!

I usually use a tuner beween the antenna and the Bitexes - that
works fine to tame the noise. Also I have fitted an RF control to
the Bitx40 that helps quieten big signals.

But if you have lots of noise in the receiver and no tuner - try
a smaller antenna on receive (it will be no good for
transmitting). If that improves things maybe you need a tuner or
an RF control.

73s John V2VOL

---
This email has been checked for viruses by AVG.

I wound a ft37-43 ferrite to get 33uh. Not as neat as an smd inductor
but I ddin't have any of them!

tim ab0wr

On Fri, 20 Apr 2018 19:53:10 -0400
"Howard Fidel" <sonic1@...> wrote:

Chris:
The parts caps I have are smaller then the resistors on the board, I
think they resistors are 0805.
It is not too difficult to solder one on top of the other.
Electrically, it doesn't matter what the size is. The inductor can be
any size, as there is no pad to fit it on, you stand it up, so 0805
is a good choice. Of course, there is nothing stopping you from uses
leaded parts.

Howard

On 4/20/2018 7:14 PM, Chris Clarke wrote:

Howard

I don't normally do SMD but this sounds like a good idea ... I'll
need to order some for this side of the pond, but which physical
SMD sizes are these components?

73 Chris
G3SQU

Thanks Arv , info much appreciated.
Norm vk5gi

This is used with the Sotabeams LaserBeam Dual variable kit. I didn't like the limited mounting options or the point-to-point of the filter kit so I made this board for my projects and had a few left over.
--
David

?N8DAH

The AGC writeup does mention that the RF gain control is assumed,
but the diagram just says "To K3 pin 14" where I assume it should say "To Wiper of RF Gain Pot"
? ??
Better yet, include the pot in the drawing.
Perhaps it should also mention the need for static discharge.
Regardless, by all accounts, that's looking like a simple and effective AGC implementation.

We get lots of thunderstorms blowing through, and I generally just try to unplug antennas
when I see them coming.? I believe I recall reading once that simply using coax offers adequate protection
if you give the braid a good earth ground.? Not sure how bulletproof that is, but my braid does have
a good earth ground.?

On p48 of July 2002 QST, it recommends something like this device:
? ??
which costs more than a Bitx40.? Is there a cheaper alternative?

Gas discharge tubes (GDT's) are often used for lightning protection on phone lines.
Seem to be available with capacitances down to? 5pf, so should work at RF.
? ??
Might well be what's in that device above.
Perhaps there's also a fuse of some sort between the antenna wire and the GDT?

Back 50 years ago, they recommended building a spark gap for use as a lightning arrestor,
the older hams who wrote about it probably had fond memories of spark gaps.
Basically a homemade GDT, using locally available air instead of some exotic gas.

Anybody know what works?
Protection schemes for this sort of thing are inherently dangerous as they are generally
untested and might give a false sense of security.? Consequences can be considerable.
Unplugging antennas is still a good idea, will still have a rig if the house doesn't burn down.

Jerry, KE7ER

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Howard

I don't normally do SMD but this sounds like a good idea ... I'll need to order some for this side of the pond, but which physical SMD sizes are these components?

73 Chris
G3SQU

Detailed instructions how to connect SDR here:?



73, John (VK2ETA)

Congratulations!? I just ordered one on 18/4/2018, so probably have another month to wait.

Don't let it get to that potential. If you are talking about lightning and such, yes, short it to ground outside. I am referring to those gentle breezes and what I call static charges. Nothing major, just enough to be annoying. -Don

That is not where you want static charges dissipating! Chokes to ground, resistors, at the antenna. All a better place for it (the fire) to happen.


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
Like us on Facebook!

Moderator – North American QRO Group at Groups.IO.

email: bill@...

In my opinion, the very best LED transmit indicator was the one that Derry Spittle (VE7QK [SK]) used in his Epiphyte QRP SSB series. That was just a 470 ohm quarter watt resistor through a small toroid and attached to a panel-mounted LED at each leg. The lead to the antenna passed through next to that resistor. That was it! When RF went to the antenna, it lit. You could easily tell if you were speaking loudly enough into the microphone, etc. Fast response, little panel space, and EASY. 73, Don

The principle idea of my AGC mod is built around the potentiometer RF gain control. It is meant to work in concert with it. As such, that potentiometer works as a static dissipation device to ground. My antennas here are both end-fed random wires (one 175 feet long, the far end up 100 feet) and are excellent static accumulators unless provided a path to ground. A 10 Megohm resistor will do that, by the way. I cannot overemphasize the desirability of a manual RF gain control, even with an AGC. I think most operators, even with the fanciest of rigs, use that control extensively. Best noise reduction device ever! 73, Don?

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Hello