Date   
Re: K5BCQ uBITX Relay Switched LPF/BPF board

Ripley
 

It does Kees. Thank you. The short take away is “sit on your hands and be patient.” I can do that.

 

Ripley

 

Sent from Mail for Windows 10

 

From: Kees T
Sent: Tuesday, September 4, 2018 5:04 PM
To: BITX20@groups.io
Subject: Re: [BITX20] K5BCQ uBITX Relay Switched LPF/BPF board

 

Hello Ripley,

The first thing is that all this still needs to be tested to see how well it works by someone with good test equipment. Warren volunteered since he has a very nice setup and I'm sending him parts. My old Marconi from the 70's just won't cut it.

Both the 6x filter and 4x filter boards are dimensionally set up to accept the QRP Labs footprint plug-in LPF and BPF filters (1.5" x 0.5"). This is to allow users to use those LPFs or design their own. The QRP Labs LPFs will handle 10W, the QRP Labs BPFs won't according to Hans Summers. Since I wanted to use the components off the existing uBITX for the LPFs and Hans does not provide a "blank" LPF board, I laid one out (attached) .....works out to 16 LPFs per "standard" 100mm x 100mm panel. 

ALL the LPF components were moved over from the uBITX board, toroids and capacitors and placed in the same locations on the blank LPF boards. The relays can also be brought over but only on the 6x filter board because it's larger. I wanted the 4x LPF board to fit in the existing uBITX location so had to go to a smaller relay. I happen to have a qty of Omron G6H-2F relays but they are 5V so I'll have to regulate off 12V .....no problem. I'm sure there are similar sized relays out there that are 12V. 

Yes, the boards are all mine and I'll make the Gerber files available once it's determined that this will work. Someone may sign up to provide boards, parts, kits. .....or you can share with others.

The idea with the 4x LPF design is to use the existing Raduino code, no changes required. However, if the 15m/12m/10m LPF is changed to 12m/10m only .....and 15m is picked up on the 20m/17m LPF (see below plots) a
small change will be required. Just don't know yet.

Hope that answers your questions.

73 Kees K5BCQ

    

 

Re: Stone Soup

Arv Evans
 

Allison

Agreed on that wide a trap.  I was playing more with the 40 meter VFO bleed through
of 4.7 to 5.0 MHz.  This for an older QST special built several years ago. 

Arv
_._


On Tue, Sep 4, 2018 at 5:28 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Arv,

Anyone that thinks they can make a trap that works over a 2mhz range is
also selling bridges.  The trap fpr 10M alone would ahve to snuff 15-17mhz.

When you get to that point a band pass filter is easier and works better.
But I repeat myself, again again again again again....

That does not help 12M with the echo at 20mhz and the 15M spurs
around 23mhz.

Allison

Re: K5BCQ uBITX Relay Switched LPF/BPF board

Glenn
 

Great work on the LPF, Kees.
I was wondering how you are mounting it to the uBITX pcb?

A screw in one corner i think. In opposite corner referring to the uBITX under, there's a section of ground plane that could have a hole drilled in it for another mounting hole. Not sure though if your pcb has space for that proposition.

Re: Does anyone have an AGC/Click kit to sell?

Wayne Leake
 

 I don't have a kit to sell.
 I have a kit, but no board.
 I was thinking making it on some perf board.
 I found a circuit, same idea, but it is two part and controls both the first IF stage and the RF amp.
 This is what I want to do.
 It is also an LED graph meter, which I don't really need as I had a bar graph meter that came with the parts kits.
 I was going to post it on one or more of the groups I am on. I may well need to buy  more parts.
 seems like I always find the need for some more parts.
 I can build the AGC setup, will breadboard it first.

 Wayne WA2YNE

Re: Stone Soup

Richard Spohn
 

Bob B., that is a very sad story. I suffered kind of the same, when I
was a novice in 1970 I was chastised for accidentally using the word
"break" on the air. I must have really offended some very sensitive
ears....and left the hobby alone for some decades. Luckily I had the
foresight to keep renewing my (shortly after the incident) general
class license. Today I am Amateur Extra, just passed that exam 3
years ago. I do not argue much with people on the air, or on this
group, since I have learned that you never win. And I truly love the
uBitx and love QRP also. Probably will never own a linear OR a yagi
in my life (wire antennas are pretty nifty to explore). Bob, it
doesn't matter what other people tell you or believe. It's what you
believe and are interested in. 73, Rich WB2GXM

On 9/4/18, Robert D. Bowers <n4fbz@...> wrote:
This thread reminds me of something I've been told by hams at least
three or four times in the last 38 years - and it brings up an issue
that I've faced throughout those years.  Some of the posts have been OK
(even encouraging), but others...

When I got my tech ticket in 1980, I scrimped and saved until I put
together $300.  I was looking for a used rig of my own, to get on the
air on HF (I had an ancient crystal mobile for 2m).  One ham told me he
had a radio I could buy - and when I got to his house offered me a KW
linear with a fried transformer, for the full $300 (tube condition
unknown).  I told him it was useless without a radio and I wasn't
interested in power like that anyway.  He was furious for me 'wasting
his time' - and told me "If you cannot afford to buy new, you don't
belong in amateur radio".  He said if I could dig up a couple hundred
more dollars, he had a nice used tube only rig (that needed repair) he'd
sell me.  I walked out on him and never spoke to him again.  He and his
buddies were, shall we say, not welcoming at the local club - where they
dominated.

That almost killed all interest.  Finally, a few years later I got
interested again, and was very much into homebrew, especially antennas.
The problem was, I still didn't have a decent radio (my hf radio was an
old tube rig - that didn't work too well and had a problem I couldn't
figure out).  When I mentioned my frustration with the radio, I was told
"What do you expect?  If you can't afford to buy new, you should
consider getting out of amateur radio!"  My radio activity went downhill
again - FAST.

I have a BITX20 V2 (or version B) - that's my newest hf rig as far as
the age of the radio.  My "good" radio is an Alinco DX-70, bought used
years ago - and it was the only working radio within my price range (had
a very small inheritance come through), although I had my heart set on a
IC-706mk2G.  I also have a softrock ensemble kit, but haven't put it
together, because I have minimal interest in the hobby anymore.

The sort of thing I consider true fun - trying to make the longest
contact possible with the minimum power (over 600 miles on less than
10mw on HF) for instance, or VHF sideband, or even 6m AM (cheap and
fun), not to mention homebrew... well, that doesn't seem as important in
the hobby as more and more and MORE POWER.  I've been stomped on enough
times by the "get a gallon to get out" club, thank you (you have that
happen time after time after time - you end up shutting off the radio in
frustration).  Funny thing, because the problems mentioned with the BITX
are made far worse by attempts at increasing the power.  Maybe people
should think about LESS power???

If I do anything amateur radio-wise, I may try to convert the BITX20 to
40m and fix the VFO so it doesn't drift.  I've always wanted a small,
low to moderate power 40m monobander for mobile use.  That might raise
some interest again.  (I bought the BITX kit unfinished and completed it
- it was sold on the proviso that I actually finish the radio and use
it.)  Something with a few watts on 40 would be nice - if the
low-power/mobile section of the band hasn't been taken over by the
kilowatt motormouths.

_*The moral of the story:*_  The BITX series of radios may be the BEST
radio a ham can afford - and being poor does NOT mean being stupid or
incapable.  Having one's rig run down is disheartening AT BEST, and
buying the latest and greatest?  Out of the question for people with
little money, even if they have brains and ability.  Reading things like
I have on this thread brings back some of the not-so-pleasant memories -
and those memories are why I've only used a few pages in a single
logbook over the last 38 years.

My 2 cents worth...

Bob
N4FBZ




Re: VK4PP uBitx LPF BANK add-on Board

Timothy Fidler
 

J1 AB are selected on zero power on relay control . Would it not make more sense for silk screening to have 15/17/20 as the no power relay ie  for daylight Sota where you want zero extra power draw and the 10/12 definition moves one block down.

IS there enough clearance to RH side of control pin line to allow a modular green plastic block header ?? - side entry to be used. This means the board can easily be disconnected and makes it all modular and professional. People make elect to go cheap an nasty on the final defacto  build but if the posn physically    clashes with the diode line so the header will not sit flush then they have no choice.  I raised this earlier with a reference to an Altronics OZ  part page. 


Suggest provide schematic to show how the new 2n3904 Tranny  fits in scheme of things.  
TEF

Re: K5BCQ uBITX Relay Switched LPF/BPF board

Kees T
 

Glenn,

Both the 6x filter board and the 4x filter board have 4 holes in them (need to be a bit smaller). I would just drill holes in the uBITX board and use nylon spacers and machine screws. 

73 Kees K5BCQ

Re: Stone Soup

James Lynes
 

It's crude, but you could treat the upper bands like a series of rock bound transmitters with a narrow tuning range(around the qrp calling frenquency, for example) and build the traps accordingly. 

James
KE4MIQ 

Re: Stone Soup

Wayne Leake
 

 I sometimes get tired of all the Know-it-alls, many of whom may know less than i have managed to forget..
 I used to hold a 2nd phone, which was later changed to a general phone.
 I try to offer some help where I can
 But not outside of what I actually know.
 I watched a youtube video about the infamous copper cactus J Pole, with the person referring to the radiating part as a dipole, where I was led to believe that it is actually a 1/2 wave Marconi.
 I decided, at tyhe time I was new to general, to build one out of aluminum, for 1 1/4 meters, and then a dual band, also aluminum, for 2 meters and 70 Cm.
 Both work well, but I will NOT claim that they are a gain antenna.
 Just a half wave vertical that is easier to have up than a vertical dipole.
 Anyways, I got interested in the BITX40 a couple of years ago. Not sure why eactly.
 Maybe the fact that I like to build, ssemble and idle with things.
 If all I wanted was HF and QRP, I could simply use my Icom 706 MK II G.
 I have 2 af Ashars BITX40's, ad 2 raduinos, plus a bare board BITX40 board that I will build as a BITX20. Being as I also bought a parts kit for BITX20.
 I am not happy with all of the arguing I see.
 I see no valid reason. People are entitled to their opinions, even if some are wrong.
 What I want to do is eventually build still another BITX, maybe for 12 and/or 10.
 Possibly one for 80 as well.
 I have no desire for getting the uBITX, as i like to be able to experment on one part at a time. Not to mention that I often get little done due to COPD and more taking its toll.
 But I do like reading about the problems and cures taking place.
 And some ideas that I can apply to the BITX20 when I get on with it.

 Wayne WA2YNE

On Tue, Sep 4, 2018 at 8:44 PM Richard Spohn <wb2gxm@...> wrote:
Bob B., that is a very sad story.  I suffered kind of the same, when I
was a novice in 1970 I was chastised for accidentally using the word
"break" on the air.  I must have really offended some very sensitive
ears....and left the hobby alone for some decades.  Luckily I had the
foresight to keep renewing my (shortly after the incident) general
class license.  Today I am Amateur Extra, just passed that exam 3
years ago.  I do not argue much with people on the air, or on this
group, since I have learned that you never win.  And I truly love the
uBitx and love QRP also.  Probably will never own a linear OR a yagi
in my life (wire antennas are pretty nifty to explore).  Bob, it
doesn't matter what other people tell you or believe.  It's what you
believe and are interested in.  73, Rich WB2GXM

On 9/4/18, Robert D. Bowers <n4fbz@...> wrote:
> This thread reminds me of something I've been told by hams at least
> three or four times in the last 38 years - and it brings up an issue
> that I've faced throughout those years.  Some of the posts have been OK
> (even encouraging), but others...
>
> When I got my tech ticket in 1980, I scrimped and saved until I put
> together $300.  I was looking for a used rig of my own, to get on the
> air on HF (I had an ancient crystal mobile for 2m).  One ham told me he
> had a radio I could buy - and when I got to his house offered me a KW
> linear with a fried transformer, for the full $300 (tube condition
> unknown).  I told him it was useless without a radio and I wasn't
> interested in power like that anyway.  He was furious for me 'wasting
> his time' - and told me "If you cannot afford to buy new, you don't
> belong in amateur radio".  He said if I could dig up a couple hundred
> more dollars, he had a nice used tube only rig (that needed repair) he'd
> sell me.  I walked out on him and never spoke to him again.  He and his
> buddies were, shall we say, not welcoming at the local club - where they
> dominated.
>
> That almost killed all interest.  Finally, a few years later I got
> interested again, and was very much into homebrew, especially antennas.
> The problem was, I still didn't have a decent radio (my hf radio was an
> old tube rig - that didn't work too well and had a problem I couldn't
> figure out).  When I mentioned my frustration with the radio, I was told
> "What do you expect?  If you can't afford to buy new, you should
> consider getting out of amateur radio!"  My radio activity went downhill
> again - FAST.
>
> I have a BITX20 V2 (or version B) - that's my newest hf rig as far as
> the age of the radio.  My "good" radio is an Alinco DX-70, bought used
> years ago - and it was the only working radio within my price range (had
> a very small inheritance come through), although I had my heart set on a
> IC-706mk2G.  I also have a softrock ensemble kit, but haven't put it
> together, because I have minimal interest in the hobby anymore.
>
> The sort of thing I consider true fun - trying to make the longest
> contact possible with the minimum power (over 600 miles on less than
> 10mw on HF) for instance, or VHF sideband, or even 6m AM (cheap and
> fun), not to mention homebrew... well, that doesn't seem as important in
> the hobby as more and more and MORE POWER.  I've been stomped on enough
> times by the "get a gallon to get out" club, thank you (you have that
> happen time after time after time - you end up shutting off the radio in
> frustration).  Funny thing, because the problems mentioned with the BITX
> are made far worse by attempts at increasing the power.  Maybe people
> should think about LESS power???
>
> If I do anything amateur radio-wise, I may try to convert the BITX20 to
> 40m and fix the VFO so it doesn't drift.  I've always wanted a small,
> low to moderate power 40m monobander for mobile use.  That might raise
> some interest again.  (I bought the BITX kit unfinished and completed it
> - it was sold on the proviso that I actually finish the radio and use
> it.)  Something with a few watts on 40 would be nice - if the
> low-power/mobile section of the band hasn't been taken over by the
> kilowatt motormouths.
>
> _*The moral of the story:*_  The BITX series of radios may be the BEST
> radio a ham can afford - and being poor does NOT mean being stupid or
> incapable.  Having one's rig run down is disheartening AT BEST, and
> buying the latest and greatest?  Out of the question for people with
> little money, even if they have brains and ability.  Reading things like
> I have on this thread brings back some of the not-so-pleasant memories -
> and those memories are why I've only used a few pages in a single
> logbook over the last 38 years.
>
> My 2 cents worth...
>
> Bob
> N4FBZ
>
>
>
>
>



Re: VK4PP uBitx LPF BANK add-on Board

Nick VK4PP
 

Thanks TIm,
I will see if Molex headers fit as per the rest of the uBitx...

Re: K5BCQ uBITX Relay Switched LPF/BPF board

MadRadioModder
 

BAP-64 is what i commonly use...


MRM

 


On Sep 4, 2018, at 10:59 AM, Lawrence Macionski via Groups.Io <am_fm_radio@...> wrote:

Kees-
Modern rigs, use diode switching to engage filters. I suggest using just 1 relay for positive switching and the output of each filter be run through diodes to a commonality. It would reduce current flow to the relays by 50%.. My thought is simple- steering up front, but where the output goes is always the same..

Years ago, I did some modifications on solid state switching VHF amplifier for VHF Engineering in Binghamton, NY.. We could drive 40 watts at 146Mhz though 4 1N914's in parallel, 25 watts through 2 of them. Experimenting required --but 2-4 1N914's are cheaper than a relay. Smaller foot print too..

--

…_. _._

Re: stone soup ingredient list, what bands and modes are usable

Tom, wb6b
 

On Tue, Sep 4, 2018 at 07:42 AM, ajparent1/KB1GMX wrote:
########################
80m harmonics, use external low pass filter
60m harmonics, use external low pass filter
40m harmonics, use external low pass filter
30m should be ok cw and SSB-digital
20m should be ok all modes
17m should be ok all modes.
15m CW ok, SSB has spur
12m CW ok, SSB has spur
10m CW ok, SSB has spur 
##########################
This is great, it means the two bands I'm interested in, 30m and 20m, are good to go. 

If I followed the various threads correctly, on 80 through 40 meters, CW was the big offender for harmonics, but SSB was not much better.

If people overdrive the TX on SSB, that is not the radio's fault. I imagine there are people overdriving and splattering all over the place with their multi grand super deluxe transceivers, by attaching all manner of add-on microphone audio processors to get more "punch".

Without any expensive equipment at all, there are multiple ways to see if you are overdriving the transmitter.

An SWR/Power meter. Increase audio until power increase flattens out and back off 20 percent.

Use a lightbulb (24+ volts, low current in parallel with a dummy load [or gasp -- antenna]) and do the same judging from the lightbulb brightness. 

Do basically the same measuring the RF voltage.

Use a nearby SDR dongle, with antenna disconnected, and look at your signal output and see where the spurs and splatter start to increase and back off the audio level.

Tom, wb6b

Re: K5BCQ uBITX Relay Switched LPF/BPF board

Paul KL7FLR
 

Tayda Electronics has these standoffs. Adhesive stickem  on base. No drilling, no machine screws needed. Several different lengths available.

 

https://www.taydaelectronics.com/pcb/pcb-support-hardware-materials/hc-5-5mm-pcb-support-html.html

 

Paul KL7FLR

Re: Stone Soup

Arv Evans
 

James  KE4MIQ

Traps can be made tunable to a small extent.  The real question is tuning range
and how to tune them accurately.  For fixed frequency traps the result can be
good, and some can be made wider at the expense of less attenuation.  LC and R
values can be adjusted for best performance, but it is not an easy thing to do. 
After deciding on best values using a simulator, they still need to be tuned using
a spectrum analyzer to insure that they are where then need to be. 

My exploration of traps and LPF enhancements was just that...exploration, with the
hope that some of my results might stimulate others to try similar ideas. 

Arv  K7HKL
_._


On Tue, Sep 4, 2018 at 8:33 PM James Lynes <jmlynesjr@...> wrote:
It's crude, but you could treat the upper bands like a series of rock bound transmitters with a narrow tuning range(around the qrp calling frenquency, for example) and build the traps accordingly. 

James
KE4MIQ 

Re: Homebrew from scratch #ubitx

MVS Sarma
 

I fear this device would be as bad as WX make.
regards
sarma
 uv3zmv


On Wed, Sep 5, 2018 at 1:27 AM <lynatmts@...> wrote:
Just converted your board files to RS274-X.  There were a couple of little frigglies that the conversion program didn't know how to handle.
Be happy to send you a copy if you like. 

Also saw your note about the audio IC?
Found they are plentiful in both thru hole and smt on ebay.
https://www.ebay.com/itm/10PCS-TDA2822M-TDA2822-SOP-8-SOP8-SMD-Two-channel-audio-power-amplifier/112331938436?hash=item1a27815a84:g:2tAAAOSwfVpYwnAy
1.39 for 10...free shipping.  Just have to waaaaiiiiiittttt foreverrrrrr.

Thanks for publishing your project! 

73

Lyn WA4GEH
/B 28.251
/AM 146.520 simplex FL10 AGL

--
"You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat."

Re: Ubitx version 4 speaker impedance?

Wayne Leake
 

 I decided to get a pair for my projects.
 Being as I have one small one that came with a parts kit, and one slightly larger one that came out of a dead Mocom 10. I like to salvage where I can.
 I used to have a good junk box, but had to start over again.
 Should work well with LM386's also...

Simple spur fix

 


This fix reduced the spurs by up to 10 db  and requires ONLY ONE part to be added.
There is big change above 10MHz in the board. There is some improvement below also.

The way I did it, CW may not work anymore will need some more mods for CW:

1. T2 - desolder the transformer wires that go to pin 3 and 5. Pin 1 has a square pad.
2. Bring out the two wires above board and join them together and solder.
3. Take a 45Mhz filter- 45M15 or  similar 2 pole - one xtal only. Solder one end of filter
to the wires of T2 pulled out. The center filter wire to ground at one end of R26. You will
see a ground via there.
4. Solder the third wire of filter to C10/R27 junction.

Thats it! This prevents the leaked TX signal that gets amplified by the 1st BiDi from getting into
the first mixer and creating havoc.

Farhan method of the same..much simpler and CW will work.

1. Remove R27
2. Solder the 45Mhz filter two extreme ends to the pads of the resistor.
3. Solder the center lead of the filter to the nearest ground. R13 is very near with a ground via.

The first method the extra filter will work in RX mode also and may help! In the second the
filter is only in the TX path..

Folks with DSA815 or better please share your feed back. The filter may work better properly
terminated etc.

Have fun!

--
Raj, vu2zap
Bengaluru, South India.

Re: stone soup ingredient list, what bands and modes are usable

David Wilcox
 

Does anyone have a simple method to take off the RF output from these rigs and safely input it to a scope to check the splatter?  I have a 60 MHz scope but don't know how to use it correctly.  That might help some of us reduce the spurs until we can learn how to do other mods. There are a lot of scopes out there to beg or borrow, mostly just sitting there in a shack or at a radio club.  There are two sitting at our club but few know what to do with them.  Sad story.

Dave K8WPE

On Sep 4, 2018, at 3:13 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

We should have some way to indicate when too much mike gain is applied.
A diode, cap and resistor watching either audio or IF or RF peak signal levels, sending that to
a Nano analog pin should be sufficient.  Firmware shows a warning in the LCD if level exceeded.
I'd go with that, and a pot for mike gain.

If you insist on ALC:  https://groups.io/g/BITX20/message/56796 

Jerry


On Tue, Sep 4, 2018 at 10:45 AM, Warren Allgyer wrote:

Your analysis is true so long as the tones, or the voice if that is your mode, do not overmodulate either the audio or the RF chain. In the case of the uBitx running 10 watts of SSB, whether it is voice or tones, one or both of those stages are significantly over-modulated to the extent they put splatter into the adjacent channels on either side. This splatter will not affect anyone listening to the SSB channel but will dramatically affect those 3 KHz up and down from that channel. The effect is far worse than on a full-featured SSB transceiver in that there is no ALC or compression to control the level.

My unit, a sample of one, over-modulates at any power level greater than 1.5 watts. Most do not care as you can hear most days on 7200 KHz..... but for those who do, you are on notice.

Re: Simple spur fix

Lev
 

Would that be a good solution to make the IF amplifier tuned? Like this? Also, change the transistors to BFS17P, this is more suited to RF.

73s de HA5OGL


On Wed, Sep 5, 2018 at 10:46 AM Raj vu2zap <rajendrakumargg@...> wrote:

This fix reduced the spurs by up to 10 db  and requires ONLY ONE part to be added.
There is big change above 10MHz in the board. There is some improvement below also.

The way I did it, CW may not work anymore will need some more mods for CW:

1. T2 - desolder the transformer wires that go to pin 3 and 5. Pin 1 has a square pad.
2. Bring out the two wires above board and join them together and solder.
3. Take a 45Mhz filter- 45M15 or  similar 2 pole - one xtal only. Solder one end of filter
to the wires of T2 pulled out. The center filter wire to ground at one end of R26. You will
see a ground via there.
4. Solder the third wire of filter to C10/R27 junction.

Thats it! This prevents the leaked TX signal that gets amplified by the 1st BiDi from getting into
the first mixer and creating havoc.

Farhan method of the same..much simpler and CW will work.

1. Remove R27
2. Solder the 45Mhz filter two extreme ends to the pads of the resistor.
3. Solder the center lead of the filter to the nearest ground. R13 is very near with a ground via.

The first method the extra filter will work in RX mode also and may help! In the second the
filter is only in the TX path..

Folks with DSA815 or better please share your feed back. The filter may work better properly
terminated etc.

Have fun!

--
Raj, vu2zap
Bengaluru, South India.

Re: Simple spur fix

Ashhar Farhan
 

I have tried the spur-zap fix. It really works. We need a big shout out to Raj, VU2ZAP. He has endlessly measured, tabulated but never given up on hunting this spur down.
I have tried it this morning too. Here are my results. I took out the R27, it is the 47 ohm series resistor that connects the tx side IF p to the front end mixer. In its place, i soldered the two ends of a spare 45 mhz filter. The ground pin of the filter was soldered to the ground end of C11.

73, f. 


On Wed, 5 Sep 2018, 14:28 Lev, <leventelist@...> wrote:
Would that be a good solution to make the IF amplifier tuned? Like this? Also, change the transistors to BFS17P, this is more suited to RF.

73s de HA5OGL

On Wed, Sep 5, 2018 at 10:46 AM Raj vu2zap <rajendrakumargg@...> wrote:

This fix reduced the spurs by up to 10 db  and requires ONLY ONE part to be added.
There is big change above 10MHz in the board. There is some improvement below also.

The way I did it, CW may not work anymore will need some more mods for CW:

1. T2 - desolder the transformer wires that go to pin 3 and 5. Pin 1 has a square pad.
2. Bring out the two wires above board and join them together and solder.
3. Take a 45Mhz filter- 45M15 or  similar 2 pole - one xtal only. Solder one end of filter
to the wires of T2 pulled out. The center filter wire to ground at one end of R26. You will
see a ground via there.
4. Solder the third wire of filter to C10/R27 junction.

Thats it! This prevents the leaked TX signal that gets amplified by the 1st BiDi from getting into
the first mixer and creating havoc.

Farhan method of the same..much simpler and CW will work.

1. Remove R27
2. Solder the 45Mhz filter two extreme ends to the pads of the resistor.
3. Solder the center lead of the filter to the nearest ground. R13 is very near with a ground via.

The first method the extra filter will work in RX mode also and may help! In the second the
filter is only in the TX path..

Folks with DSA815 or better please share your feed back. The filter may work better properly
terminated etc.

Have fun!

--
Raj, vu2zap
Bengaluru, South India.