Topics

BitX HW-16: full break-in high power ri

Gordon Gibby
 

 Many years ago, as a teenager I had a full break in HW 16 ;  had to give it up for my next rig. 

 I’m starting to think there is a way to re-create it, using two UBitx,  and the carcass of a HW 100   

 Use one of the UBitx as the receiver;  
 Use the other as the exciter to drive the last two stages of the HW 100 — gives  100 W output,  although I’ll add my relay daughter board, those two stages add additional useful filtering 
 Add in some diode networks, or maybe a pin diode if required, and some slick fast bias changes on the vacuum tube finals,  which can be moved in and out of cut off, class C and class AB1....
One raduino  can provide all the frequencies for both rigs;  relays only have to change state when you Change bands;   Transistor control of Vcc wires ; One of them is always receiving, the other is always “transmitting “ —  just instantaneously biased into operation and back out  
 Lots of shieldiing each uBitx  in some shielded compartment 



 Change a just few things and it does digital & regular single side band as well 

 Relatively inexpensive, high-performance full break in high power radio,  Computer controllable, digital frequency control 

 Use some digital filter when using CW 

Gordon 

Tom, wb6b
 

On Fri, Sep 6, 2019 at 09:33 AM, Gordon Gibby wrote:
full break in HW 16
Brings back memory's of when I was first interested in Ham radio. The description of that radio/transmitter with dual conversion and crystal filters was something that made me want that rig. I did not become a Ham until much later when I hooked up a down converter to a Radio Shack general coverage shortwave receiver and started following a group of Hams, on 2 meters (I had to slope detect), that would meet after work at a near by Denny's restaurant. I became interested in joining in, they were frequently discussing interesting radio/technical things, so I contacted (by mail) one of the Hams, he lent me some more gear, I studied, got my tech license, and could join in of the work commute and Denny's.

Back to full break in mode. Tubes are still popular in the audio circles. Wonder if it would be possible (or valid) to create a stand alone tube RF pre-amplifier for receivers that would be bullet proof against (at least in terms of not burning out) being attached to a coax line while a transmitter is powered up on the same coax. This could be great for near by lightning strikes, too. 

Then you could put a tee connector in your coax to directly connect to the vacuum tube pre-amp.

To some extent this tube pre-amp may be sold more on the nostalgia of the gold old tube days. And unfortunately some marketers may start selling it on the claim that if gives your radio the much improved "tube" sound quality. But it might be a cool idea. Especially if the tube sticks prominently out of the top of the box, so you can see the red filament glow, and maybe a ring of blue LEDs at the base to add to the cool tube effect.

Joking aside, it may possible there could be a place for a vacuum tube in RF front ends. 

Tom, wb6b

Gordon Gibby
 

Well, I could probably hijack the front end of the HW 100 and use it for exactly that purpose!


On Sep 6, 2019, at 17:19, Tom, wb6b <wb6b@...> wrote:

On Fri, Sep 6, 2019 at 09:33 AM, Gordon Gibby wrote:
full break in HW 16
Brings back memory's of when I was first interested in Ham radio. The description of that radio/transmitter with dual conversion and crystal filters was something that made me want that rig. I did not become a Ham until much later when I hooked up a down converter to a Radio Shack general coverage shortwave receiver and started following a group of Hams, on 2 meters (I had to slope detect), that would meet after work at a near by Denny's restaurant. I became interested in joining in, they were frequently discussing interesting radio/technical things, so I contacted (by mail) one of the Hams, he lent me some more gear, I studied, got my tech license, and could join in of the work commute and Denny's.

Back to full break in mode. Tubes are still popular in the audio circles. Wonder if it would be possible (or valid) to create a stand alone tube RF pre-amplifier for receivers that would be bullet proof against (at least in terms of not burning out) being attached to a coax line while a transmitter is powered up on the same coax. This could be great for near by lightning strikes, too. 

Then you could put a tee connector in your coax to directly connect to the vacuum tube pre-amp.

To some extent this tube pre-amp may be sold more on the nostalgia of the gold old tube days. And unfortunately some marketers may start selling it on the claim that if gives your radio the much improved "tube" sound quality. But it might be a cool idea. Especially if the tube sticks prominently out of the top of the box, so you can see the red filament glow, and maybe a ring of blue LEDs at the base to add to the cool tube effect.

Joking aside, it may possible there could be a place for a vacuum tube in RF front ends. 

Tom, wb6b

Curt
 

Lets see, the ubitx was advanced because many inexpensive rigs only do cw. Funny thing I mostly have done cw with the ubitx, but the early qsos were ssb.

I imagine somewhere there is a ubitx that does qsk, more likely a homebrew one. seems like a bit of work. BTW, study the qsk in some modern rig. especially the k2 100w PA to see how it gets the high negative voltage bias. 

Funny thing my novice hw16 still lives. The pfr3 I have pretty much does the same thing.

I did build a solid state xtal transmtter and used it with my tubed hr20.

73 curt

Tom, wb6b
 

On Fri, Sep 6, 2019 at 06:24 PM, Curt wrote:
my novice hw16 still lives
Interesting, I was looking around at sites that featured old Heathkit photos and product information. Found this link. Looks like someone is reviving Heathkit in Santa Cruz California. Maybe a nostalgic Dot Com millionaire? Much better than when Zenith was slapping the Heathkit name on cheap consumer products.

http://www.heathkit.com

Tom, wb6b

Ashhar Farhan
 

If you guys can locate, look for the bitx20a manual. It has a Tayloe T/R switching system. The other mod will be to keep the lpf relays powered up.
The heaviest lifting is what we can do to avoid the t/r thump that results from charge on the rx IF amps that take time to discharge.
- f

On Sat 7 Sep, 2019, 10:12 AM Tom, wb6b, <wb6b@...> wrote:
On Fri, Sep 6, 2019 at 06:24 PM, Curt wrote:
my novice hw16 still lives
Interesting, I was looking around at sites that featured old Heathkit photos and product information. Found this link. Looks like someone is reviving Heathkit in Santa Cruz California. Maybe a nostalgic Dot Com millionaire? Much better than when Zenith was slapping the Heathkit name on cheap consumer products.

http://www.heathkit.com

Tom, wb6b

Thomas Sharka
 

Tom, wb6b
 

On Fri, Sep 6, 2019 at 10:51 PM, Ashhar Farhan wrote:
look for the bitx20a manual. It has a Tayloe T/R switching system
Hi,

I found some reviews of the bitx20a. Did not find a schematic, yet. However, I found this CW transceiver designed by Dan Tayloe that has a couple of mosfets to cut off the RF to the receiver section when transmitting. 

https://www.qrpkits.com/files/SchematicsFFSDRv1-1large.JPG

Is this similar to what you are referring to with the bitx20a design?

Tom, wb6b

Tom, wb6b
 

On Fri, Sep 6, 2019 at 11:12 PM, Thomas Sharka wrote:
https://www.vintage-radio.info/heathkit/
Cool site. Fun to look once again, in the context of the era of Heathkit kits and the early space race technology, the electronic designs I poured over learning electronics design. 

Then think of now, when microprocessors have almost replaced transistors as the fundamental unit of designs. Thinking about what a big deal Ham TV was. Now you have a portable wireless TV camera and video screen in your pocket. And you can talk on it and read the news, too boot.

Tom, wb6b

Jim Willis
 

Same here Tom. I lived near Huntsville when I was first licensed, WN4CCA. I sent off for a NASA technical bulletin – “Telemetry”. Latest in high tech. Interviewed at IBM Huntsville, they showed me their navigation system comprising three microprocessors “voters” and an analog “patch panel” navigation computer. I was hooked!

 

73 de KX4TD, Jim

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Tom, wb6b
Sent: Saturday, September 7, 2019 3:52 AM
To: BITX20@groups.io
Subject: Re: [BITX20] BitX HW-16: full break-in high power ri

 

On Fri, Sep 6, 2019 at 11:12 PM, Thomas Sharka wrote:

https://www.vintage-radio.info/heathkit/

Cool site. Fun to look once again, in the context of the era of Heathkit kits and the early space race technology, the electronic designs I poured over learning electronics design. 

Then think of now, when microprocessors have almost replaced transistors as the fundamental unit of designs. Thinking about what a big deal Ham TV was. Now you have a portable wireless TV camera and video screen in your pocket. And you can talk on it and read the news, too boot.

Tom, wb6b

Jerry Gaffke
 

Tom,

You need to poke around a bit further on qrpkits.com
    https://www.qrpkits.com/bitx20a.html
Schematic is in that first assembly manual listed.

Second paragraph here mentions it plus a couple other options with regard to TR switches:
    https://www.qrpkits.com/bitx20a.html

For single band use, Kang's TR switch is very simple:
    https://groups.io/g/BITX20/topic/32744828
But the inductor and cap must be series resonant at the freq of use, so won't work on the multiband uBitx.

All of these T/R switching schemes have been around for decades.

Jerry, KE7ER



On Sat, Sep 7, 2019 at 12:36 AM, Tom, wb6b wrote:
On Fri, Sep 6, 2019 at 10:51 PM, Ashhar Farhan wrote:
look for the bitx20a manual. It has a Tayloe T/R switching system
Hi,

I found some reviews of the bitx20a. Did not find a schematic, yet. However, I found this CW transceiver designed by Dan Tayloe that has a couple of mosfets to cut off the RF to the receiver section when transmitting. 

https://www.qrpkits.com/files/SchematicsFFSDRv1-1large.JPG

Is this similar to what you are referring to with the bitx20a design?

Tom, wb6b

Jerry Gaffke
 

Correction:  
Second paragraph here mentions it plus a couple other options with regard to TR switches:
  https://groups.io/g/BITX20/message/39746

Jerry, KE7ER


On Sat, Sep 7, 2019 at 08:28 AM, Jerry Gaffke wrote:
Second paragraph here mentions it plus a couple other options with regard to TR switches:
    https://www.qrpkits.com/bitx20a.html

Jerry Gaffke
 

As John, K0JD pointed out in post
    https://groups.io/g/BITX20/message/70894
the TenTec Argosy was using rectified RF to create the high DC voltage
required for a PIN diode T/R switch.  As proposed in post 32109 some 30 years later.
Later in that Argosy discussion we find that two of the diodes in the manual are drawn backwards.

If I were to do T/R switching for the uBitx, I'd first try something like what's in the Argosy.
For the Bitx40, use Kang's much simpler single band solution.

Jerry, KE7ER

Tom, wb6b
 

On Sat, Sep 7, 2019 at 08:28 AM, Jerry Gaffke wrote:
For single band use, Kang's TR switch is very simple:
That is an interesting circuit. So it looks like the series resonate circuit is a low impedance at 40 meters passing the received RF to the receiver amplifiers. Then, when the transmitter is keyed up the diodes begin to conduct and the effective low impedance of the diode in that situation, disrupts the series resonate circuit and the transmit power into the switch circuit now only/mostly sees the relatively high impedance of the 52 PF capacitors and the voltage the receiver needs to withstand is limited by the clamping function of the diodes.

If I interpreted correctly how this circuit works, very clever. Actually, if I didn't interpreted it correctly, still very clever.

 https://groups.io/g/BITX20/topic/32744828

Tom, wb6b

Tom, wb6b
 

On Sat, Sep 7, 2019 at 06:34 AM, Jim Willis wrote:
IBM Huntsville, they showed me their navigation system comprising three microprocessors “voters” and an analog “patch panel” navigation computer.  I was hooked!
I can imagine what that was like. I did not work in the space race, but, as a kid, a friends father worked for Autonetics and he would bring us to their employee open house events and we would get to see all this amazing technology set up on display in various labs. For a kid it was mind boggling to see this stuff and in many lucky instances, someone was there to try to explain it to a kid. 

I just looked at this video where a new tech person gets to talk with an IBM Huntsville engineer from the day. He really seems to get a feeling for the technology of the day and the amazing things accomplished at that state of the art.

https://www.youtube.com/watch?v=6mMK6iSZsAs

What it must have been like to thrust a monstrous machine off the earth with a huge controlled explosion, with a control technology that had a main program loop cycle time of two seconds, to actually keep this monster on track.

Tom, wb6b

Jerry Gaffke
 

Tom,

The Kang approach is in fig 2 of the W7ZOI article pointed to by post  https://groups.io/g/BITX20/message/70861
That article mentions Roy Lewellen, W7EL, and his "Optimized Transceiver" in the Aug 1980 QST
as a possible source for what W7ZOI considers this "standard" T/R switch.
Here's a 2018 treatment of T/R switches by W7ZOI, the Kang approach is figure 1:
    http://w7zoi.net/tr-qrp.pdf

Oh, and post 70861 was from Tom, WB6B.
I've probably seen the circuit over the years as well, 
never quite realizing how it worked.

Jerry, KE7ER

Tom, wb6b
 

On Sat, Sep 7, 2019 at 06:59 PM, Jerry Gaffke wrote:
Kang approach is in fig 2 of the W7ZOI article pointed to by post  https://groups.io/g/BITX20/message/70861
Hi,

That Wes Hayward article is pretty good. I'd recommend people read it, including myself.

I think at the time I found that article we were trying to figure out just how much like a PIN diode the 1N4007 rectifiers behaved. And if 1N4007 diodes from different manufactures might be different in regards to the "PINness" of their diodes. I skimmed right past the "Resonate T/R Switch" description. 

Tom, wb6b

Tom, wb6b
 

On Sat, Sep 7, 2019 at 06:59 PM, Jerry Gaffke wrote:
Here's a 2018 treatment of T/R switches by W7ZOI, the Kang approach is figure 1:
    http://w7zoi.net/tr-qrp.pdf
A quick look at this article looks very good. I'm in the process of learning the Eagle Schematic capture and PCB design package. That package includes Ngspice. I can use the LTSpice schematic included in the article as a practice exercise for learning Eagle and Ngspice. As well as more about the operation of the T/R switch.

Just a thought though, if you were willing to comprise a little attenuation of the receive signal into the receive circuit and waste a little heat in a resistor while transmitting, maybe just using a resistor to limit the current flowing into the back to back diodes and a series resistor to the input of the receive circuit to keep the current there well below what would damage the receiver input, would work. That would work for a multi band transceiver. 

If you don't force the input of the receiver first stage to be 50 ohms and let it be significantly higher, the main resistor from the antenna connector to the back-to-back diodes could be a fairly high resistance. At HF the noise contributed by the receiver first stage is low compared to the main source of atmospheric noise, so a little signal loss wold not be a problem. (Of course, the answer to this is probably already covered in some part of these linked articles I have not read yet.)

I image there are receivers out there that don't bother to to supply 50 ohms, on receive, to the antenna terminal. I wonder how far you could deviate before the coax could create a 1/4 wave notch filter. I'm sure I'd end up cutting my coax just to the length so it would be a perfect 1/4 wave length at my favorite net's frequency.

Tom, wb6b

Don--AE4DW
 

On Sat, Sep 7, 2019 at 12:42 AM, Tom, wb6b wrote:
On Fri, Sep 6, 2019 at 06:24 PM, Curt wrote:
my novice hw16 still lives
Interesting, I was looking around at sites that featured old Heathkit photos and product information. Found this link. Looks like someone is reviving Heathkit in Santa Cruz California. Maybe a nostalgic Dot Com millionaire? Much better than when Zenith was slapping the Heathkit name on cheap consumer products.

http://www.heathkit.com

Tom, wb6b
Trying not to veer too far off topic, but I remember seeing that resurected heathkit site several years ago, before they had any products to offer. It does look like they got it off the ground.

As another of those hams who started their operating experience with an HW-16 (circa 1976), and then upgraded to an HW-101, I still, to this day, appreciate what Heath stood for eons ago.

Jerry Gaffke
 

Yes, you could compromise receiver sensitivity without much downside if atmospheric noise still exceeds front end noise.
Though it is nice to be able to at least listen in when using a crummy antenna, such as a few feet of magnet wire
thrown across the floor.

In that 2018 paper on his website, W7ZOI simulates what a VNA would see using LTSpice.
When you build hardware, would be nice to verify the results using a cheap VNA such as
     https://www.alibaba.com/product-detail/Original-2-8-Touchscreen-50KHz-900MHz_62232701280.html
as discussed in     https://groups.io/g/nanovna-users

As mentioned previously in the forum, a VNA would not do the job of an Antuino
when sniffing out signals in a working radio.  The VNA can only see the results of a signal
that it injects into the circuit, at a frequency of its choosing.

Jerry, KE7ER


On Sat, Sep 7, 2019 at 11:44 PM, Tom, wb6b wrote:
On Sat, Sep 7, 2019 at 06:59 PM, Jerry Gaffke wrote:
Here's a 2018 treatment of T/R switches by W7ZOI, the Kang approach is figure 1:
    http://w7zoi.net/tr-qrp.pdf
A quick look at this article looks very good. I'm in the process of learning the Eagle Schematic capture and PCB design package. That package includes Ngspice. I can use the LTSpice schematic included in the article as a practice exercise for learning Eagle and Ngspice. As well as more about the operation of the T/R switch.

Just a thought though, if you were willing to comprise a little attenuation of the receive signal into the receive circuit and waste a little heat in a resistor while transmitting, maybe just using a resistor to limit the current flowing into the back to back diodes and a series resistor to the input of the receive circuit to keep the current there well below what would damage the receiver input, would work. That would work for a multi band transceiver. 

If you don't force the input of the receiver first stage to be 50 ohms and let it be significantly higher, the main resistor from the antenna connector to the back-to-back diodes could be a fairly high resistance. At HF the noise contributed by the receiver first stage is low compared to the main source of atmospheric noise, so a little signal loss wold not be a problem. (Of course, the answer to this is probably already covered in some part of these linked articles I have not read yet.)

I image there are receivers out there that don't bother to to supply 50 ohms, on receive, to the antenna terminal. I wonder how far you could deviate before the coax could create a 1/4 wave notch filter. I'm sure I'd end up cutting my coax just to the length so it would be a perfect 1/4 wave length at my favorite net's frequency.

Tom, wb6b