Re: RD16HHF1 in the uBITX #ubitx

 

Jack,
We have decided to go down this road also, we got a 5 pack, and hot air station, going to do a toaster oven reflow oven, and maybe a George Forman preheat grill…I am working on some ideas for these rabbit holes….what I do best…

My first try at one of these boards with hot air….without preheat….very predictable…board was not warm enough, nice little balls....talked with a former production manager at a electronics manufacturer….got some good ideas…no way can we duplicate how its done in the ‘real’ world…but, then, I am not trying to do that.

Also have got one of those tetra whisper aquarium pumps and hooked it up to one of those ‘extra’ syringes left in my room at my resort stay before the new year….so I have been picking up large SMDs and inhaling small ones….

I went to my storage junk box and pulled out some drawer slides…..and ordered one of those usb scopes on monday? amazon had a lightning deal for 30 bucks….

We are going to dive into the deep end of the pool next month….

After our Builders Group finishes the new Antenna Analyzer, then we move onto BitX mods….any and all of them, and then for at least a few mods…done from the perspective of a club designed circuit, then use a CAD program and create the gerbers, then order the boards….whole life cycle….show them they can do it….by having them do it.

maybe start with polarity protection circuit, definitely some power supplies, probably AGC…..not because it hasn’t been done….but, exactly for that reason…most don’t think they can do any of this….if it is something they want to have…then I see some desire to build it….if they build it….some will learn how it works….when they have to make it work

Jack, besides the circuit in the center, if you notice the two pads at the bottom of each column of practice random devices by size? Well you should get some flavor of something besides infinite if you put a multimeter there….as the devices in a column seem to be in series with the pair of pads.  A check on soldering skills in each column.

gotta slow down….

but not until we also write some sketches….

I am going to need a bigger bucket for my list.

I can see how wrong I was when I working my last few years in electronics (mid nineties) and encountered modifications that required some large format SMD rework on a small scale….and I became an instant combatant….as I was doing in home repairs and battling a worsening tremor…I can overcome all those big problems today for pennies on the dollar back then….and go to youtube college and talk group tutoring….

Craig
KM4YEC



On Feb 20, 2018, at 10:47 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:

I've run into the SMT inertia as well. AT our club meeting next month, I am setting up three solder stations with three of these:


and I'm going to have the members each solder as small a part as they can handle. I think once they do it, they will see how easy it really is. BTW, when done and voltage is applied at the bottom center of the wheel, the LED's should light up. The whole thing cost $2.29 with free shipping! Once they see how easy it is, then I'm going to push how cheap the SMT's are.

Jack, W8TEE



From: Eric KE6US <eric.csuf@...>
To: BITX20@groups.io
Sent: Tuesday, February 20, 2018 9:13 PM
Subject: Re: [BITX20] RD16HHF1 in the uBITX

Tough for many to work with because they won't. Homebrewers are going to have to  learn a few SIMPLE and CHEAP tricks to solder devices like this. I've been using this process for several years without difficulties.
A syringe, a small tweezer to place the parts, solder paste and a $20 embossing tool (heat gun) from WalMart or any craft store. It makes the 20-QFN or any other SMT easy. Especially with a PCB or breakout board for the part. Dozens of suppliers make them for every package type. Several of them on OSHPark for dirt cheap and a modest lead time.
I showed my 7 year old granddaughter how to do it, and she begs me to let her do more. The only hard part for her is squeezing the solder paste out of the syringe. She's tiny and doesn't have the hand strength to do it. The paste is thick and the hole in the syringe is very small.
Steady hands and a good magnifying light and you have everything you need. I'm not 7, I'm 75. I wouldn't care if all thru-hole parts disappeared tomorrow, though I might have a problem keeping my boatanchors on the air.
Stop whining about SMT (not you, Jerry) and give it a serious try. It's fun and it's easy. If you make a mistake, heat the part up, scrape it off and start over. No vias to worry about destroying to clean out holes.
Eric KE6US

On 2/20/2018 2:00 PM, Jerry Gaffke via Groups.Io wrote:
The best solution would be to get the transmit power amp chain to behave,
giving uniform power out across the bands.

Failing that, the PE4312 attenuator would be good, though a tough package 
for many to work with.  Almost impossible to just dead-bug into place.

Perhaps we could adjust the value of the emitter resistors at Q90 and Q911/Q912 depending
on the band selected.  Add an extra emitter resistor in parallel, connected to ground only when
a 2n7002 FET is turned on.  Use the band select relaly control lines TXB and TXC to
control the FET's.  Cost of maybe $0.25 in volume.

Jerry, KE7ER


On Tue, Feb 20, 2018 at 12:46 pm, RCBoatGuy wrote:
The AD8367 is more than twice as expensive as the PE4312, though the AD8367 datasheet does show how to implement AGC with it using 2 additional chips.  So if you want to include AGC with programmable attenuation, the AD8367 may be the way to go.

However, for less than the cost of a single AD8367 you can put two PE3412's in series to get attenuation up to 62dB.  

Not sure what the best trade-off is.  Depends on your needs and price range, I guess.




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