Date   

Re: Low Pass filter inductor question. #filters

Mike Short <ai4ns.mike@...>
 

You need to switch both ends, preferably grounding the unswitched filter.


--
Mike
AI4NS


Re: Ubitx - using Amateurradiokits.in AGC #ubitx

Eddie Esserman
 

John,

Where did you upload the schematics and procedure?

I've been off trail for a few days.

Eddie


Re: Low Pass filter inductor question. #filters

davedt1e@...
 

Thank you Howard and Allison.  I know this is just kindergarten stuff to you all,  but that switching really had my brain tied in knots for a while!


Re: Low Pass filter inductor question. #filters

Howard Fidel
 

That's the idea.

On 10/1/2018 8:49 PM, davedt1e@... wrote:
I think I've got it.  Does this look right?



Re: PTT switching for amp

iz oos
 

Maybe you may want to add a PTT (RF relay sequencer).


Il 26/set/2018 15:31, <m0clscarl@...> ha scritto:
Hi, can someone tell me a simple way to add a ptt switching circuit for my amp please? Can I just use pins from the transmit relay? 

Thanks.


Re: Low Pass filter inductor question. #filters

davedt1e@...
 

I think I've got it.  Does this look right?


Re: ND6T AGC

Don, ND6T
 

I agree with you about getting the 5 volts from the 7805. It only pulls a couple of milliamperes and won't be noticed. That switching power supply, on the other hand, is a known noise source. A great comb generator.
I did not catch your placement like Nick did. Midst the 45 MHz filter? It should be in the receive RF path. Placing it elsewhere will disrupt any filter impedances. Trouble waiting to happen, certainly. This is an RF AGC. It keeps the signal within manageable levels throughout the receiver.
All of mine are physically mounted on the rear of the RF gain control up on the front panel. Close to the AF feed from the volume control, the 5 volt source, and the RF path. As a result, they work boringly well.
You would not be able to detect the 0.6 dB attenuation without good instruments, certainly not by ear. Movement of the volume control should not change AGC operation at all. Something else is going on. Do you have an oscilloscope? If so, check on the input side of C1. There should only be audio.
73,
Don


Re: ND6T AGC

Joe Puma
 

Yes I was thinking that as well. I’ll see if I can move it. Gonna try to add a power ground as well since the only ground is coming from the pin connector. 



On Oct 1, 2018, at 6:49 PM, Nick VK4PP <nickpullen@...> wrote:

Joe.
My personal concern is where you installed the AGC, it is right in the middle of the 45Mhz filter... I prefer to put the AGC over on the other side near the first LPF relay.
Could be noise from your power supply getting into the 45mhz If....
Maybe...

73 Nick


Re: uBitx FT8 problem

John P
 

On Mon, Oct 1, 2018 at 06:36 PM, John P wrote:
Split mode on WSJT is a checkbox on the left side of the window about 1/3 of the way down
Oops! Ignore that! I was thinking of DxCommander which is what WSJT uses to control my radio.

In WSJT, to find the split mode setting, go to "Settings" then click on the "Radio" tab. On the right side of the screen about 2/3 of the way down, you'll see three choices for split mode: "None", "Rig" and "Fake It". The meaning of the first 2 should be obvious. I haven't tried it, but I believe the 3rd choice will play with the frequencies on a radio that doesn't support split mode (i.e. one with only one V FO) as if it did.

--
John - WA2FZW


Re: ND6T AGC

Nick VK4PP
 

Joe.
My personal concern is where you installed the AGC, it is right in the middle of the 45Mhz filter... I prefer to put the AGC over on the other side near the first LPF relay.
Could be noise from your power supply getting into the 45mhz If....
Maybe...

73 Nick


Re: uBitx FT8 problem

John P
 

Split mode on WSJT is a checkbox on the left side of the window about 1/3 of the way down. 
--
John - WA2FZW


Re: PTT switching for amp

Lee
 

Who said it was PTT but that is what the connection on the amp is called.  In my old HF Packer amp there was a jumper that could be moved for CW. Some have replace the jumper with a switch.  The HF packer amp did not chop syllables.  I am building my 70w amp for 20m  SSB.  I don't care about AM, FM, or CW.  I will go ahead!
--
Lee - N9LO  "I Void Warranties"

 


Re: ND6T AGC

Joe Puma
 

Hi ND6T,

All good questions. The BCI filter was in before the AGC. The waterfall was wonderful. Removed spurs and other emissions. I’ll send a nice screen shot of just the BCI filter. The tap is near the 45mhz crystal for IF out  so the BCI and agc will effect what tap sees. The AGC is after the BCI so it’s receiving a cleaner signal, I figured that would be the logical thing to do? 

 If I unplug the AGC (see OP pic) and jump in/out I’m back to a clean signal no spurs. Seems like the AGC is adding something back in. I’m powering the AGC and Raduino from a 5v buck regulator. One of those popular ebay items that seems to be used on radio projects. image1.jpeg

I thought J1 disables AGC completely. But good to know there is some attenuation as I do have a okay signal but with some added spurs, they are visible In the pics I provided.  Another odd thing is when I raise the volume the last 15% of the max volume changes the attenuation dramatically 

I’ll check voltages. Maybe wire up the 7805. 


Joe


On Oct 1, 2018, at 4:21 PM, Don, ND6T via Groups.Io <nd6t_6@...> wrote:

The AGC is a simple wide band attenuator, When properly powered and with a short across J1 there should be only about 0.6 dB attenuation (barely measurable). No artifacts.
Check your wiring and your voltages. While it is possible that a component has failed, it is unlikely.
Yes, the SDR display looks very lame. Did you try installing it before you did the AGC mod? Best to do one modification or experiment at a time to avoid confusion, no matter how small a change.
There are too many variables to properly address from afar. Where did you derive your 5 volts?, Did you install a manual RF gain control? Did you make any voltage measurements? Did you install the filter before you did the AGC and the IF tap? By "spikes" do you mean spurious signals (frequency domain) or impulses (time domain)? When you tune the transceiver do you hear whistles? Do those spikes change when you replace the antenna with a termination?
73,
Don


Re: PTT switching for amp

Timothy Fidler
 

This is not PTT , it is called COR - carrier operated relay and you will get sick of it soon. 

It cannot be used with any RF format that has a constant carrier like FM or AM,
It give the relays in the system a real hammering,
It cannot be used with CW without a time out circuit and

it will chop introductory syllables in some cases... but go ahead...


Re: Low Pass filter inductor question. #filters

davedt1e@...
 

Ok...I see what I did wrong now.   That's embarrassing...Ha!

So to be clear... Is it sensible to just switch the 40 meter out of the circuit (for 20),  and leave them both in for 40? Would that be too much,... I think the phrase is, "insertion loss"?   Or better to keep them entirely separated?

Thanks for your patience!


Re: PTT switching for amp

Lee
 

I am also building a 70w amp and this is what I am working on.  The circuit on the left I use as a RF indicator so I and see my Mic modulation in my radio,  I am making another with the relay circuit for inside the amp.


--
Lee - N9LO  "I Void Warranties"

 


W0EB's uBITX with 5" Color "mouse" Screen 1st QSO!!! #ubitxcw #ubitx

Jim Sheldon
 

Finally got time enough after all the work on the 5" color TFT touch/mouse/keyboard display on our BITeensio card in one of my uBITX rigs that I was tuning around 20 meters a few minutes ago and heard CT9/OM7LW on 14.014 working split 1 up. 

Gave my uBITX a good test of functions - put it in split, set the TX frequency to 14.015, mode to CW and called him.  Measured 4.89 watts out and I got him first call.  I don't believe the 599 signal report he gave me, but then I don't believe in S meters either.  He WAS quite strong on my little PAR EndFedZ 40-20-10 meter antenna which is only about 15 feet or so above the ground and quite close to the roof of the house.  I normally use this antenna only for testing so I'm super pleased that this particular uBITX's first QSO was a DX station on Madeira Island!  Don't get too much better than that!

Using the mouse and that screen, setup for split was super easy, took only seconds and I made the QSO. 

I had spent the previous hour and a half changing out the fan on the case for a bigger one that moves more air to keep the 3.3V heat sink cool.  I do believe I have my hamfest demonstration rig working (have to give a presentation this coming Saturday at the Wichita, KS hamfest on this and the 2.8" color display version.

Jim, W0EB


Re: ND6T AGC

Don, ND6T
 

The AGC is a simple wide band attenuator, When properly powered and with a short across J1 there should be only about 0.6 dB attenuation (barely measurable). No artifacts.
Check your wiring and your voltages. While it is possible that a component has failed, it is unlikely.
Yes, the SDR display looks very lame. Did you try installing it before you did the AGC mod? Best to do one modification or experiment at a time to avoid confusion, no matter how small a change.
There are too many variables to properly address from afar. Where did you derive your 5 volts?, Did you install a manual RF gain control? Did you make any voltage measurements? Did you install the filter before you did the AGC and the IF tap? By "spikes" do you mean spurious signals (frequency domain) or impulses (time domain)? When you tune the transceiver do you hear whistles? Do those spikes change when you replace the antenna with a termination?
73,
Don


Re: Low Pass filter inductor question. #filters

ajparent1/KB1GMX <kb1gmx@...>
 

Yes, both legs must be switched.   The reflection of the if the unterminated filter will be across the 
one in use.   At a bare minimum you have to test to insure it will work but generally its going to
be trouble.

Its not a shared ground.  Its the shared hot!  What does a 40M filter look like at 20M?
What does a 20M filter look like at 40?  Hint the 20M will pass 40M signals (and possibly harmonics),
But the 40M will not pass any 20M signals.  So a filter that does not pass 40M across a 20M filter
has to have bad effects.

You  need two sets of contacts.  

Allison 


Re: ND6T AGC

pa0mlc73@...
 

Hello Joe,

I did build the ND6T AGC circuit on veroboard; I noticed the same signal decrease; I can only figure that the impedance of the grounded emitter 2N3904 input is too low and consequently is loading too heavily on the audio line.
I did replace the 2N3904 with a FET amplifier and the high impedance of the gate is causing no load to the audio line.
I do not hear any spikes on the signal with the AGC operating; do you have the RF-gain potentiometer (1-5 kohm) mounted?; when an ungrounded antenna is being used, the drain of the AGC FET is high imp on the antenna side and high imp on the RX side;this may cause static buid-up; I recommend a galvanic connection to ground (1-100kohm) of the antenna (can be parallel to the FET).
ND6T mentions the RF-potentiometer to be used with the AGC-board.

73,

Marcus
pa0mlc

Op ma 1 okt. 2018 om 16:14 schreef Joe Puma <kd2nfc@...>:

 

So I installed the ND6T and I think its working but the results are questionable. It seems to decimate my signal completely only allowing the littlest of signal in. I have to turn up the volume all the way to hear anything. With it inline it obviously ruins the experience of the IF out and waterfall as it reduces RF on the whole viewable band. My IF tap might need to be moved somewhere else, not sure if it can be put before the AGC as that’s a different stage before 45mhz crystal and mixing right? (shooting in the dark here).  We can address that later.

 

Another thing I noticed as the ND6T AGC introduced some spikes back into the signal path. I put the AGC after the BCI filter thinking it would be better to AGC a cleaner RF signal without all that AM IMD. I’ll post a pic of the bard layout so you can see my solder work and where I put the components.  I don’t think I messed up there but its odd that when the AGC is in place the overall signal drops at least 60-70%. Yes I can some signals but weaker signals just disappear. I figured that my signal wouldn’t be attenuated maybe even amplified if signal was lower then expected and then just attenuate the stronger signals.

 

 

This is with the AGC inline by disabled with the jumper across JP1. There are some noticeable spikes when inline compared to when its not. I don’t have a current comparison without it inline.

 

 

 

This is a shot with the AGC enabled. Jumper on JP2. The signal is mostly gone. I was playing with the volume control and where you do see signal further down the water fall is when I had the volume knob turned up. You can see the evenly spaced spikes too.

 

 

 

 

 

 

 

 

Sent from Mail for Windows 10

 

From: Joe Puma
Sent: Monday, September 24, 2018 7:00 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC

 

Thanks everyone. I was able to secure a kit, thanks Mark!

 

 

Joe

 

Sent from Mail for Windows 10

 

From: Dennis Zabawa
Sent: Monday, September 24, 2018 1:46 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC

 

You can get a board ONLY from: https://vk4pp.blogspot.com/p/nd6t-agc-de-vk4pp.html