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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 1st Aug 2018, 9:37 pm   #1
kellys_eye
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Default SBL-1 Mixer

Yes, the ubiquitous mixer device.

There are schematics of the innards around but has anyone ever made a comparable device from discrete parts that works as well as the original device? If so, what parts did you use?

I ask as I have a requirement for a few of them but their cost seems to be rather excessive given the experimental reasons I want them for - and I don't exactly need the full 500MHz bandwidth either.

I've considered modern alternatives (ADE-1?) but even these seem to be 'costly' for what they really are (this is the 'cheapskate' coming out in me!)
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Old 1st Aug 2018, 10:33 pm   #2
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Default Re: Sbl-1

If economy is desired, why not use a NE602/NE612 ic for the job. Conversion gain, and
no inductors to wind.
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Old 2nd Aug 2018, 1:07 am   #3
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Default Re: SBL-1 Mixer

Yes I blew one up Saturday night a few months back and didn’t want to wait for a new one. I used two FT37-43 toroids (trifilar 8 turns wound) and 4x 1n4148 diodes. Worked absolutely identically as far as I could tell at 14MHz in a DC downconverting SDR receiver I built to monitor CW on 20m. Search for “1n4148 dbm”’ on google for schematic.

The 1n4148’s were matched however. The matching process is buy a roll of 100 and stuff 1mA through, measure voltage drop with a DMM and then bin them in groups. When you have four close, stop

Think they take about 7dBm drive for LO in that config and there is around 6dB loss. The termination has to be set up as per SBL-1 so benefits from a diplexer. Although I used a 100n cap in series with a 51 ohm resistor and it wasn’t unhappy.
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Old 2nd Aug 2018, 5:42 am   #4
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Default Re: SBL-1 Mixer

Some info here that may be of use:

http://kitsandparts.com/drm.php
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Old 2nd Aug 2018, 6:22 am   #5
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Default Re: SBL-1 Mixer

Yes, I've made diode ring mixers before the packaged ones became available. HP bought small trifilar transformers from Pulse Engineering and later had its own transformers department wind our own designs. HP also sold matched sets of four wire-leaded Schottky diodes before the diode quad-in-one-package types came along.

In the 1990s, John Birkett advertised some minicircuits DBMs he had in stock. They were like SBL1s, but not quite the same, they may need more oscillator power. Because they were not 'real SBL1s' he'd priced them lower than the real thing. They were Minicircuits RAY-3s ! Their super duper ultra high level mixer. I phoned John and explained what they were. He explained that the market wanted SBL1s or MD108s and would only pay less for anything else. I suppose it's like the current market for Dansettes I bought a lot of the RAY-3s. John assured me he was happy at that price and was making his usual profit on what they'd cost.

The kitsandparts board uses an HP/Avago quad diode array.

Avago have recently bought out Broadco and then decided to change name to broadcom. They have also decided to stop making small RF parts, so all the HP/Avago diodes, amplifiers etc have just stopped being made. This has dropped a lot of the RF industry in the you-know-what. Lots of firms are having to redesign products rather frantically. There is a lot of anger and resentment and a number of firms have issued blanket bans on designing in any Broadcom parts. Companies have got their buyers looking for any remaining stocks of various parts to help tide them over. So you might have trouble getting the diode array for that mixer.

NXP, M/Acom, TriQuint (now calles Qorvo) still do small RF semiconductors.

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Old 2nd Aug 2018, 6:59 am   #6
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Default Re: SBL-1 Mixer

The 160m transverter I built many years ago had one of my homebrew discrete balanced ring mixers in it - you will find it in a Tech Topic article from the 1970s. No idea of how it compared with the SBL-1, or what ferrites I used, but it did the job at the time.

And Terry, I saw your spectrum analyser article in the latest RadCom. Not got round to reading it in detail but looks good stuff - though probably a bit too advanced for me with all that surface mount stuff in it. I have one of the G3PMK analysers, the classic from RadCom in the 1980s but it doesn't get much use now.

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Old 2nd Aug 2018, 7:06 am   #7
David G4EBT
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Default Re: SBL-1 Mixer

The term 'costly' is of course subjective, but there are scores of SBL1s for sale on e-bay, both new and used but tested, for under a fiver 'buy-it-now' post free, which doesn't sound overly expensive. (As always - others offered at ludicrous prices in excess of £35.00).
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Old 2nd Aug 2018, 8:09 am   #8
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Default Re: SBL-1 Mixer

I'd stopped looking at the auction sites for SBL-1s as the last time I did they were the ridiculously priced versions but I've speculated on a couple to see what they are really like.

Thanks for the tips'n'tricks on making your own. I'm surprised to see 1N4148's being used as I thought schottky were required - having said that you can also get (practically!) bandoliers of them at knock down prices and if you follow Mr Bungles matching procedure you're 'sorted'.

The various links to sites with information are also useful - I found one that had DIY mixers on a SA and impressed by the results.

As ever, there's always more than one way to tackle the subject and I appreciate the input from all contributors - thank you.
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Old 2nd Aug 2018, 10:54 am   #9
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Default Re: SBL-1 Mixer

To note I don't know how good a mixer it was I built from a measurement perspective because I don't have an SA (yet!) and was filtering out all the mixer products I wasn't interested in by design.

Another option I've seen is use a couple of BAT54SL's instead of 4x 1n4148's as they are relatively well matched dual schottky diodes. https://www.onsemi.com/pub/Collateral/BAT54SLT1-D.PDF

Of course I didn't because I didn't have any available on a Sunday morning

Replying to Radio Wrangler: The moment Broadcom appears on something, everyone runs away! Rightfully so. I've dealt with them on NIC issues on HP servers and their silicon is broken and no one wants to fix it. We ended up buying new NICs for all our servers thanks to this for the mere sum of just over £45k.
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Old 3rd Aug 2018, 1:28 am   #10
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Default Re: SBL-1 Mixer

If you're a member of the GQRP Club, there was an article in Sprat 144 about making your own SBL-1's.

The diodes used were either BAS40-04 double diodes (Schottky) or LL4148's.

The cores used were 2843002402 binocular or T37-43's.

There's also a pcb design not much bigger than an SBL-1
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Old 3rd Aug 2018, 11:00 am   #11
David G4EBT
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Default Re: SBL-1 Mixer

A nicely written article in SPRAT 144 (2014). Time moves on, so I guess the first challenge is finding the components, notably the 'pig-nose' binocular cores, but there is a source on ebay in the UK at four for £3.99 post free. (Two are required per unit). As to the diodes, there is the option of using either two BAS40-04 dual schottky diodes or four SMD LL4148s. (SMD version of the 1N4148).

Farnell have the BAS40-04 @ 22.8p each, min qty 5 (4,000 in stock!):

http://uk.farnell.com/multicomp/bas4...t23/dp/1797826

The LL4148 SMD diodes can be sourced on e-bay at £2.99 for 100 +99p from a UK supplier.

Ironically, the hardest item to find now that Maplin have ceased trading seems to be genuine 1mm Veropins. There are countless offerings on e-bay which use 'Veropin' as a generic term (a la 'Thermos', Hoover' etc), but they're not genuine Vero - they're little more than small 'tacks'. Whether or not Veropins are even made now, I've no idea. Sure, we can improvise, but for me it goes against the grain when 'improvise' morphs into 'compromise'.

Sometimes using tat might not matter, but I've attached a couple of pics (unrelated to SBL1s) in which genuine Veropins would have been fine, but fake ones, (bought from a reputable small UK company and described as 'Veropins'), had two shortcomings: No ribbing, so until soldered weren't secure, and secondly, the heads were so large that they had to have 'flats' ground on them so they didn't short out. (It was only a prototype PCB, which I later scrapped, along with the pins). When my Veropin stock runs out, I'll resort to using 1mm brass wire, slightly flattened at the lower end to grip the board when inserted, but as a self-confessed fusspot, that's a tad 'bodgertonics' for my liking. (When the only tool in your toolbox is a hammer, everything starts to look like a nail).

Back on track - you certainly need a steady hand, a keen eye and a strong magnifier to etch and construct the PCB for the SPRAT home-brew SBL1s! The PCB is just 27mm long x 12mm wide and each of the two versions has twelve 'lands' and eight terminal pins onto which to solder the components.

Great if you're up for a challenge, otherwise, SBL1s at under a fiver each on e-bay start to look rather tempting!

Have fun.

"Use what talents you possess - the woods would be very silent if the only birds that sang were those that sang the best".

Henry Van Dyke.
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Old 3rd Aug 2018, 1:12 pm   #12
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Default Re: SBL-1 Mixer

The 'pig nose' cores are available at RS and for much less than £3.99 for 4. (just over 10p +VAT each in lots of 25).

And the BAS40-04 are 6p +VAT each if you don't mind buying 100 of them.

Not sure of the delivery/collection options in the UK, so the other choice "may" be cheaper (I get free delivery here in Oz).

I've made the pcb's from Sprat, they're not that bad.

And for a fiver, you could make a dozen or more clones.
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Last edited by Terry_VK5TM; 3rd Aug 2018 at 1:16 pm. Reason: Add diode info
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Old 3rd Aug 2018, 5:47 pm   #13
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Default Re: SBL-1 Mixer

If you can find a manual for the Swan 100MX/102/103 series they had a neat way to make SBL1 like DBMs. They built them on 16 pin DIL IC headers by putting transformers at each end and the diodes between the central 8 pins.

I will post a picture if I can find one, otherwise it's dig deep in the shed to find an actual one.
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Old 3rd Aug 2018, 7:41 pm   #14
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Default Re: SBL-1 Mixer

That actually jogged a memory. From June 1987 QST, a Doug DeMaw classic “Build your own MCM ICs”...

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This is reprinted in ARRL QRP Classics pp45-49.

Not sure it is cost effective though as the DIL headers are £3.03+VAT each. Might be able to use turned pin sockets.

Last edited by MrBungle; 3rd Aug 2018 at 7:44 pm. Reason: A decade out on the article date!
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Old 3rd Aug 2018, 8:16 pm   #15
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Default Re: SBL-1 Mixer

Oooo... I like those 16-pin header versions. Very 'me'.

And some great component 'finds' from Terry - many thanks for that!
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Old 3rd Aug 2018, 10:55 pm   #16
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Default Re: SBL-1 Mixer

Gah I just spent two hours building and debugging the DeMaw 40dB audio amp circuit.

It is quite frankly trash. I redesigned it in the end and got my 40dB rather than -10dB. And forget making little modules like that. It’s hell. In fact I am getting rid of the book before I burn any more time on it.
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Old 4th Aug 2018, 4:24 am   #17
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Default Re: SBL-1 Mixer

And for those that haven't seen the insides of a real one:

http://www.qrp4u.de/docs/en/Components/index.htm
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Old 4th Aug 2018, 11:43 am   #18
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Default Re: SBL-1 Mixer

That article shows just how tiny the cores are in the metal package- I think that the SRA-1 has a taller can to accommodate transformers with effective response down to VLF. There's also a useful caveat about NE602-style devices and their signal handling limitations- the price to pay for very simple PP3-capable applications!

A good example in this thread of an early DBM application using (appropriately) Ge diodes, with notably large pot-core transformers necessary for a receiver tuning down to 10kHz;

https://www.vintage-radio.net/forum/...d.php?p=892230
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Old 4th Aug 2018, 3:08 pm   #19
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Default Re: SBL-1 Mixer

The likes of Amidon:

http://www.amidoncorp.com/43-materia...perture-cores/

still offer their range of 'classic' binocular ferrites.

You don't strictly need a two-hole ferrite for winding the balance-transformers: two single-hole beads side-by-side work rather well.: I've built bifilar transformers for the crystal-filter in SSB generators using this technique and found no difference compared to a binocular.

In the past I also worked on a range of HF/VHF power-amplifiers whose 'balanced' push-pull driver/output transformers were made from two parallel lengths of silver-plated copper tube about 3/4 inch diameter, with sets of ferrite rings threaded over them, and silver-plated copper plates silver-soldered to the ends to provide a 'single turn' - PTFE-insulated coax was then threaded through the holes to provide the primary winding.
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Old 9th Aug 2018, 7:19 pm   #20
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Default Re: SBL-1 Mixer

NE 602 and their ilk. Just avoid.
I won't go there.

Bitterly disappointed to find them in FT897, FT857 and I suppose by extension (I don't have one) the FT817.

Diode rings - depending on type used are mostly very good, when homebrewed, if well matched diodes are used. A tickle of DC will balance them for best carrier rejection but that will change over temperature most likely.

Has anybody used them as an AM modulator? Add DC for setting carrier level and then apply the modulation?
A bit like balancing a pencil on it's point?

Last edited by Jon_G4MDC; 9th Aug 2018 at 7:29 pm.
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