Better sound from an SDR (such as a Flex) or other TX that uses a balanced modu

[KA8WTK]

Hi Steve,
  I am just guessing, but would that circuit output ideally be fed directly to the DBM in a rice box bypassing the audio section of the radio?

Bill

[Pete, WA2CWA]

With many of the current transceivers on the market  today with DSP circuitry, they don't use a "balanced modulator". Like my IC-756 PRO II, I haven't used my mike input since I bought the rig. My audio input into the rig goes directly to the Accessory socket when there is a modulator input connection.

[WA2SQQ]

Steve, if you were to make a PCB, would you use surface mount components, or standard leaded components? One way or another I'm going to start gathering the parts. Also, I see there a several resistors that aren't standard values. Are their value that critical, or can you substitute standard values? I guess it would be easy enough to use some miniature trim pots to get them spot on.

[KA8WTK]

Pete, my radios are older than yours. 

[AG5CK]

Is sw301 a bypass for the filter? I would like to use this circuit with my ts440 that currently has a 7.5k filter. It would be nice to narrow things up when necessary.

[W9BHI]

SW-301 changes the output audio phase.

[AG5CK]

Thanks. After looking at the datasheet for the tl074 I think I see some light through the darkness.

[steve_qix]

Steve, if you were to make a PCB, would you use surface mount components, or standard leaded components? One way or another I'm going to start gathering the parts. Also, I see there a several resistors that aren't standard values. Are their value that critical, or can you substitute standard values? I guess it would be easy enough to use some miniature trim pots to get them spot on.

Nothing surface mount (at least not yet).  It's just so much easier to build using through-hole components.

[KD6VXI]

Steve,

you should talk to the clown that designed this thing....  WAY too many parts.

And those odd values!




Sounded good on K2SDR today


--Shane
KD6VXI

[steve_qix]

Steve,

you should talk to the clown that designed this thing....  WAY too many parts.

And those odd values!




Sounded good on K2SDR today


--Shane
KD6VXI

Thanks for the report     Good conditions on 75 this afternoon for sure!

Just so everyone knows what Shane is talking about - I was assembling this circuit today while I was in QSO, and "complained" about the designer (me) that there were too many parts in the circuit.  That's where a PC board will make it easier.  In reality, there aren't THAT many parts, but I was growing tired of soldering at that point.

Regards,  Steve

[WA2SQQ]

Thanks for the short chat last evening on 75. You mentioned that you have the "critical value parts" - let me know how much you want and I'll get some $$ off to you. That might be the only difficult part of this project.

[AG5CK]

Between the junk box and mouser I have everything but the1n34a. Im going to hit the local surplus store next week. I may end up trying some different substitutes and see if I can hear any difference.

[w4bfs]

... I have everything but the1n34a.....

how ironical is this ... the first hobbyest solid state electronic components were 1N34a germanium point contact diodes and a few similar transistors (2N109, CK722, 2N34, etc) .... so many projects were developed for these

nice work Steve and others

[KD6VXI]

The negative clipper diode is not at all critical. 

Steve:  While I was listening to you, I had a friend in the shop.  Newly minted General class.

You keyed and started talking, and he picked his head up and looked at the screen.  When you made the statement about 'who designed the thing', he looked at me and said 'I want that!'.

Shortly after, he was on classeradio site taking in all he could...

Nice station, and it makes a great advertisement.  What where you running, class e or sdr?

--Shane
KD6VXI

[Pete, WA2CWA]

Between the junk box and mouser I have everything but the1n34a. Im going to hit the local surplus store next week. I may end up trying some different substitutes and see if I can hear any difference.

In a pinch, sometimes you can use the base to collector leads of an old germanium transistor. 

[steve_qix]

The negative clipper diode is not at all critical. 

Steve:  While I was listening to you, I had a friend in the shop.  Newly minted General class.

You keyed and started talking, and he picked his head up and looked at the screen.  When you made the statement about 'who designed the thing', he looked at me and said 'I want that!'.

Shortly after, he was on classeradio site taking in all he could...

Nice station, and it makes a great advertisement.  What where you running, class e or sdr?

--Shane
KD6VXI

That was the class E rig.  The Flex is the receiver and will be the VFO for remote operation.  Otherwise, for local operation, I'll use my homebrew VFO.

[WD5JKO]

Steve,

   I heard you guys on 3873 and then 3875 last night. Timmy was doing a job to the 3873 Texas "no traffic" net on 73. He made a good Old Buzzard transmission.

You were as loud as he, and comfortable copy at around 10-20 /9 on my Flex 3K.

I have a Flex 5K coming, also with 2nd RCVR and ATU. Should have it by this weekend...

After that I will have a Flex 3K and an Icom R-75 4-Sale.

Jim
Wd5JKO

[WA2SQQ]

For any of you who are going to build one, I created the shopping list. Those components noted with an * are critical values, and should not be changed according to Steve.

Value          Qty   Component
0.001   10   CAP
0.0015 *   1   CAP
0.0022 *   1   CAP
0.01           1      CAP
100uf   2   CAP
25uf          1       CAP
3300uf   2   CAP
47uf          1       CAP
1N34A   1   DIODE
1N4007   4   DIODE
LM7812   1   IC
LM7912   1   IC
TL072   1   IC
TL074   1   IC
2K POT   1   POT
5K POT   1   POT
560          2   RES
10K          3   RES
17.4K *   1   RES
2.2K          2   RES
2.87K *   1   RES
220K          2   RES
22K          2   RES
28K          1   RES
4.7K          2   RES
6.81K *   1   RES
8.45K *   1   RES
9.31K *   1   RES

[KG6PQQ]

Appreciate that , ordering today.

[W2PFY]

Are all resistors 1 watt? Maybe that is spelled out on the schematic but I writing this on the fly. In addition, would the first person who orders all the parts include an approximate cost?

Thanks Terry

It would also be great to see examples of your build. I have built all sorts of homebrew tube stuff but never solid state.

[WA2SQQ]

No, 1/4W is more than enough

[WA2SQQ]

Are all resistors 1 watt? Maybe that is spelled out on the schematic but I writing this on the fly. In addition, would the first person who orders all the parts include an approximate cost?

Thanks Terry

It would also be great to see examples of your build. I have built all sorts of homebrew tube stuff but never solid state.

Here's how I buy my standard components ...
http://www.ebay.com/itm/3120pcs-156-Value-1-4W-1-Metal-Film-Resistors-Assortment-set-1-ohm-10M-ohm/182366765338?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D41395%26meid%3D6f20dc258ad94235919a45e5f19652b3%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D182409997607

[steve_qix]

Good list!  I made some comments/quick edits.  I did not verify that every part in the circuit is there, but I did verify the critical parts and made notations where I edited.

Thanks!!

Value          Qty   Component
0.001   10   CAP (Edit: 2 are critical values - need to be very close to .001)
0.0015 *   1   CAP
0.0022 *   1   CAP
0.018 *     1      CAP  (Edit: this cap was missing from your original list)
0.01           1      CAP
100uf   2   CAP
25uf          1       CAP
3300uf   2   CAP
47uf          1       CAP
1N34A   1   DIODE
1N4007   4   DIODE
LM7812   1   IC
LM7912   1   IC
TL072   1   IC
TL074   1   IC
2K POT   1   POT
5K POT   1   POT
560          2   RES
10K          3   RES
17.4K *   1   RES
2.2K          2   RES
2.87K *   1   RES
220K          2   RES
22K          2   RES
28K   *      1   RES (Edit: this part is a critical value)
4.7K          2   RES
6.81K *   1   RES
8.45K *   1   RES
9.31K *   1   RES

[WA2SQQ]

Steve
I have several TL071's which I believe are 1/2 of the 072's. No reason I can't use 2 071's in place of the 072, right?

[w1vtp]

FYI:
For the Flex Series:
Flex 5000 has single(unbalanced) and balanced mike inputs.
Flex 3000 has single(unbalanced) mike input.
Flex 1500 has single(unbalanced) mike input.
Flex 6300 has single(unbalanced) mike input.
Flex 6500 and 6700 have single(unbalanced) and balanced mike inputs.

Just a thought; since many SDR-type rigs run off 12 volts DC, it would have been convenient to design your circuit to run off the same 12 volt line.

Peter - thanks for the info.  You always have the right info at the right time. Anybody have the circuit Peter is referring to?  Gotta be a simple  DC to DC converter - probably a switcher. It would be nice to be independent from the AC line in case one is operating under say a 12 volt battery.  That might be better put in a separate thread

Al