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Another project, only semi-wacky. Browning receiver adapter.

nomadradio

Analog Retentive
Apr 3, 2005
6,938
11,065
698
Louisville, KY
www.nomadradio.com
You may have seen the "wacky" project with a Bump-Bump roger beep-in-a-box. Might never build another of those.

This one is a bit less wacky. Have enough parts to build six of these.

Nearly all of them are already promised, so that may be all of them that ever get built. Not trying to sell them here. Not today, anyway.

Depends on how expensive they are to build. Once I have a record of the labor we spent to make six of them I'll have a way to decide.

The first one always takes a lot more time, since you're working out where to put things and how best to fabricate stuff. Besides, I don't like selling unhatched chickens. Bad juju.

This toy plugs into the transmitter socket of a Browning receiver and an external transmitter of your choice.

AFs1uu.jpg


Why? Several possible reasons. Browning transmitters get more expensive to restore every year. The 'ping' is inside the receiver, not the transmitter.

People have asked for this trick off and on for decades. This is not the first incarnation, but the result of lessons learned from the previous attempts. The first version, circa 1999 had two coax pigtails on it, and a socket for the antenna coax.

Too clumsy. Needed its own wall-wart for power. Nice try.

Next attempt was to install the whole thing inside the Browning receiver. More compact, but a lot of trouble to install. And using an original Browning transmitter required setting a switch for 'factory' or 'other' type transmitter.

This one is powered by the receiver. You have to add ONE black wire (or the color of your choice) to pin # 3 of the transmitter socket. This wire lets the adapter 'borrow' the 6.3-Volt AC heater power from the receiver. No more wall wart.

M9Zbz1.jpg


This has one additional advantage, simplicity. Turn OFF the Browning receiver, and the box becomes a barrel connector. If your external transmitter is a transceiver, like a Cobra 29, a Yaesu FT-101 or a RCI2995, it will now be connected to the antenna all the time.

Turn on the Browning receiver and the relays inside the box go "click", and the green LED comes on. The antenna is now connected to the Browning's antenna socket. The external-transmitter radio gets connected to the antenna only when you key the mike. The green LED goes dark while you're keyed and the red LED tells you that it's working this way.

OGe38f.jpg


And if you fancy using the factory Browning transmitter the normal way, just unplug this toy and hook up the stock transmitter the normal way.

Shot more pics of the assembly process, but this post is already getting long.

Time to write up a "how to" with the schemo and parts list. You'll probably have one sooner by just building your own than waiting for us to build some and market them.

73
 
Last edited:

So, here's part one of the DIY Browning transmitter adapter.

First, the schematic:

onFCWI.jpg


it's getting late, so I'll add another post with some description of what's what.



The BOM (bill of materials) or parts list should paste right in here with no hiccups. I hope.

N O M A D R A D I O

1615 Bardstown Road Established 1975
Louisville KY 40205 Chris Reifsteck, Proprietor

FILENAME: BRNTXADA.PRT 7/1/17 CR
Parts list for the 2017 Browning transmit adapter.

Enclosure:
1) Hammond 1590B 4.4" x 2.4" x 1.2" die cast box

Hardware:
1) #4-40 x 1/2-inch long threaded spacer
2) #4 tooth-washer style ground lugs
14) #4 x 5/16 in. 'keps' philips machine screw captive LW

Connectors:
1) UHF bulkhead male
2) SO239 bulkhead female
1) 86CP-8 male octal plug
1) 86 shell
16 in. 5-conductor jacketed cable
1) Heyco bushing for control cable
2) 5mm LED bezel

Electromechanical:
2) G2R-2 5VDC DPDT relay

Diodes:
1) 5mm green LED
1) 5mm red LED
1) 1N5401
3) 1N4001
2) 1N4148

Transistors:
1) TIP120
1) 2N3904

Capacitors:
1) 4700UF 16V axial
1) 10uf 50V radial
1) 10pf ceramic disc

Resistors:
1) 150 ohm 1/4W
1) 470 ohm 1/4W
3) 1k 1/4W
1) 10k 1/4W
1) 0.5 ohm 1W
1) 4.7k 2W

Pretty sure it's complete.

More later

73
 
Looks like an RF keying circuit driving a darlington, throwing the contacts of a T/R switch. Pretty slick , I like it. Thanks Nomad
 
Yeah, the TIP120 darlington gets just a bit warm carrying the parallel coil current of two 5-Volt relay coils. About 130 F. A smaller transistor would get hot. Using two of the DIP style relays keeps the profile of the enclosure thinner than a single 3-pole or 4-pole would permit. I really wanted to use the bulkhead-type male coax plug attached to the case. If it were much taller than the flange on the coax connector, threading it on and off would get awkward.

As for that "more later" remark, I just got a call from a customer. Looks like shop traffic will keep me busy for another day or two. I'll write up a circuit description.

Later.

73
 
Last edited:
So, here is a revised schemo of this toy. I frequently skip adding callout numbers for the parts in a simple gadget like this. As soon as I promised to explain how it works my idiot light came on. Putting a number on the callout of each part sure does simplify describing what I'm talking about.

Yeah.


1GJSc6.jpg



To start, the rectangular symbol at the top is the round 8-pin "octal" tube-socket style plug. This is the same connector found on the end of the factory-original transmitter's receiver cable.

Pin 7 has a jumper wire to pin 8 because the receiver's internal speaker won't work without it. Had something to do with the older transmitters' "PA" feature.

Pin 1 is ground. Pin 2 is for the "On The Air" light below the speaker. Grounding this pin turns on the light.

Pin 3 has been modified by adding a wire from the receiver's 6.3-Volt AC heater supply. Unless you are using a pre-1965 Browning receiver. Browning originally sold "selective call" accessories that plugged into this socket and would hold the speaker squelched until the correct tone from a mobile radio was heard, and the decoder would activate the speaker. Don't think Browning sold too many of those, and the later "Golden Eagle" radios did not have this pin connected at all. We're using it to power the adapter box. R1 serves to limit the turn-on surge to charge the main filter cap C1, and also as a fuse if there is a short in the adapter box. D1 is a 3 Amp rectifier. They're about the same price as a smaller rectifier, and it should not care about the surge current from the large filter cap.

Turn on the receiver and C1 will now charge to about 8 Volts DC.

The 8 Volts DC on C1 is connected directly to the hot side of both relay coils and to R2. R2 has two jobs. It limits the current to the green LED D6 to about 5 mA and supplies base current to Q2. R8 limits the base current into the base of Q2 to about 2 mA or a bit less. This is more than enough to turn on a high-gain darlington transistor like a TIP120. Q2 carries the coil current for both relays into the collector, and out the emitter to ground. D8 is a "catch" diode that absorbs the reverse-polarity pulse that will come out of the relay coils whenever they are turned off. Reverse polarity is generally unhealthy for transistors, even if it doesn't last for long.

The relay contacts labeled "NO" will all now be closed, since the relay coils are powered. This closes the circuit from pin 4 to pin 5 of the receiver plug. Opening this circuit mutes the Browning receiver while transmitting. The "NC" side of the relay pole connected to pin 2 of the receiver plug is now open, keeping the "OTA" light off.

The "NO" side of the relay pole connected to the three coax sockets connects the antenna to the receiver's antenna input.

When you key the mike on the radio connected to the "XMTR" socket with a coax jumper, your carrier passes through C2. The small capacitance value of 10 pf serves to limit the RF current feeding into R4 and then into the two small 1N4148 signal diodes D2 and D3. They serve as a half-wave voltage doubler. This is to make the adapter as sensitive as possible to a radio with the carrier turned down. Also serves to prevent relay chatter if the radio's negative modulation peaks are excessive. D2 and D3 will rectify the RF to DC and charge the 10uf cap C3 through R5. R5 serves to limit peak diode current charging C3. R6, a 10k resistor serves to discharge C3 within a hundredth of a second (or so) after you unkey. The two series 1N4001 rectifier diodes D4 and D5 hold the voltage across C3 to a max of around 1.3 Volts DC. The idea here is to prevent a high-power radio like a Yaesu FT101 or RCI2995 from overdriving the "unkey" transistor Q1. The voltage drop from base to emitter for Q1 is a fairly constant 6/10 of a Volt. This way the voltage drop across R7, 150 ohms is also a fairly-constant 6 or 7 tenths of a Volt. That way the base current into Q1 remains a constant 4 mA. This is a safe drive level for Q1 and allows it to be highly sensitive to a low carrier power without getting hammered by 150-Watt modulation peaks.

--- Fair warning --- This feature is still not tested. Gonna try it with a bigger radio and see that my calculations hold up in practice. This toy is still a work in progress.

With 4 mA into the base of Q1, it will provide a near-dead short from collector to ground. This will shut off the green LED D6, and remove the base current feeding into Q2. The relays will now drop to the power-off "normal" states. The receiver is muted by breaking the circuit from pin 4 to pin 5 on the octal plug. The "OTA" light comes on, and the antenna socket is now switched away from the Browning's antenna input over to the transmitter's coax jumper attached to the "XMTR" coax socket.

R3 will now have nearly the full 8 Volts feeding into it through the two parallel relay coils, putting about 6 mA through the red LED D7, until the transmitter is unkeyed and both relay coils are once again energized.

Biggest reason to want this thing powered from the Browning receiver is that if you simply turn off the Browning, your transmitter is now connected to the antenna as if through a barrel connector, and it can be used in the normal way without shuffling coax jumpers.

The intent was to simplify the hookup and operation of the thing as much as possible. Having to install a wire inside the receiver to pin 3 of the receiver's transmitter socket is the only drawback, and a better solution than powering it from a wall wart.

73
 
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