The AM Forum

The AR-88 I'm using did not have the signal strength meter option built into it.  I'd like to install one, externally.

How much voltage should be measured across the I.F.?  Is that the best place to get meter voltage?

Now, I -know- this will generate lots of discussion - it always has, but I'll make this declarative statement, anyway...

50uV = S-9.

What would you use for a meter shunt, and how would you calibrate it (y'ou', being use collectively, of course).

(http://www.thorneyhill.freeserve.co.uk/ar88.jpg)

This is what it looks like, with no meter.  (Not the actual receiver I'm using, mind you).

I'd take a gander at some schematics of receivers with a similar layout circuit-wise, such as Hammarlund, Collins, National, and see how they get their S-meter to run?

Usually there is a rectifier creating DC...

                 _-_-bear

I think it was only the later models that got the S-meter. An actual AR-88 with stock S-meter will work from right to left instead of the common left to right. Now, a friend of mine visited the guy who helped design this receiver, he said that the S-meter scale was hand drawn and was only in 0-5 scale. It was a very plain looking meter. Having said all that, there are all kind of circuits that were used to install into the AR-88. I'll have to check my 1940-49 CD of QST. I thought I saw one in there. Also, check the surplus conversion books for stuff that came from WWII

There's an indication on the schematic of where to install the S-meter.  It's on the cathode of one of the IF toobs.

The meter is indeed backwards-reading (IE the pointer rests to the right with the power off).  S-meters do NOT measure IF voltage.  They generally read the plate current of one of the IF toobs.  That's why many are backwards reading - the stronger the signal, the more the AVC voltage, and hence the lower the plate current. 

Some receivers have S-meters that are driven by another toob in a VTVM arrangement.  The National NC-300 is one such receiver where the grid of a 12AU7 picks off AVC voltage and the S-meter reads the plate current of the 12AU7.  Again this is a backwards reading meter.

There's no reason you couldn't install an S-meter using a conventional meter; look at typical receiver skizmatics for examples.  The NC-183 and/or HRO would be good examples, they use conventional meters with no zero adjust.  The GPR-90 is another, it essentially reads screen current of one of the IF toobs (this one, however, uses a zero adjust pot).

I scored several NOS AR-88 S-meters at the Fredneck hamfest a few years ago.  Put 'em up on eBay and they brought $300 a piece!  That helped GREATLY with the XYL's attitude towards the hobby, esp after I treated her and the kids to a nice dinner with some of the spoils  ;D

You should design a LED bargraph signal strength display since it's going to be external. 70's and 80's technology!

Geoff

Have you considered an external meter?  This is one I originally make up for my S-53. It uses a twin
triode in a bridge circuit,  and operates off of the AGC voltage.  It's similar to the handbook designs,
except both sides of the triode are used for each leg of the bridge.

I'm thinking about using it on my AR-88.


Pete  k1zjh

(http://i271.photobucket.com/albums/jj129/k1zjh/finished-meter.jpg)
(http://i271.photobucket.com/albums/jj129/k1zjh/side-view-wiring.jpg)

Well Geoff, I am wondering why you care?  S9 @ 50 uv. is true only where the meter is calibrated on these old tube receivers.  It is very unusual to see the same microvolt reading giving you S9 anywhere else.  If you can hear em well then give them a Q5 report.

Geoff,

I believe that the original meter was a 5 ma fs that rested on the right peg.
There was a 100 ohm pot that bridged the meter movement to ground (one terminal connected to the + meter term and the variable term of the pot went to ground and the other terminal of the pot was unterminated). The 6SQ7 (V5 - 1st IF) had R20 (100 ohm) and C74 (4700 pf) from cathode to ground.  The + side of the meter and pot connected at the junction of R20 and C74.

Does that make sense??

I used a Weston model 301 Type 30B in my AR-88D but have a meter that I think may be correct to install.

By the way, I thought RCA had the wires already run for the 88's they didn't install meters in.

73,

Joe - KB9R

The SX-28 meter is 5 ma. and rests to the right

The AR and 88, eh? 

I recall Ozona Bob, W5PYT talking about those for hours.    And hours.  He'd talk about the quality of the nickel-plated escutcheons for at least 45 minutes. 

Ed said:
Heh, heh, he talked about any radio like that for hours! ;D

Geoff,  I found an SX-28 S meter for my AR-88 and it fit and works great.  Since most AR-88s were built without them in the  first place, the SX-28 meter is scarce, but much more likely to turn up.   

73, Bob W9RAN

Thanks, everyone, for your comments regarding the AR-88 Receiver and the advent of adding an S-meter.
 ;D
I'd like to update everyone on what's going on with that receiver (and me) since that posting. 

#1) I'm no longer on the air, on a regular basis from San Antonio, TX, on 75m Yay-Am.:o

Currently, am "cliff-dwelling" in an apartment :'( here in Houston, TX, :-X driving for a hot-shot delivery company.  At least bills are getting paid, and there's food in the fridge.  Life is good.  ;)

HF mobile is -strongly- on my mind and I am working in that direction again, in the new (to me) vehicle.  Mounting a headache rack on the 2006 F-150 is priority, but when that happens, a couple of 'tabs' will be welded at the area where the headache rack is bolted to the top-rail of the bed of the pick-up.  I'll probably install a 'gum-drop' mount, with an SO-239 at the bottom, and 3/8x24 threaded female on the top, an impedance matching coil, an 18" stainless steel rod, and then the 75m hamstick with whip adjusted to 3.875Mc.  The 75m Hamstick has ~25kc bandwidth.  I have dreams of installing a 2500w DC inverter, running DC to the filaments of the 6146's (wiring them in series) and doing the same with the 807's, solid-stating the rectifiers and running the Viking II mobile, with a T/R switch, and an Alinco DX-70TH xcvr for the AM Rx as well as ssb xcvr.  The DX-70 covers from 160 through 6m, a 220MHz rig, and a dual-band V/UHF rig, will have me HF mobile from 160 through 450MHz.  Hey, I said they were dreams ;)

#2) the AR-88 has developed a problem. ??? Seems as if the IF oscillator circuit has ceased to function.  According to Jim/WD5JKO (where I -got- the AR-88 in the first place) this isn't the first time this has happened.
 Jim has the receiver again. (there just ain't room for me, the YL -and- a collection of boat-anchor gear in a 1-bed-room apartment) and maybe, when we move into a house (hopefully in September) I'll have enough room to have an actual ham-shack, again.  When that happens, I'll put the 250TH x 250TH rig back on the air.  It's currently still in San Antonio, 200 miles to the west.  :-\

Speaking of the AR-88 and Ozona Bob/W5PYT, Jim/JKO tells me that this particular AR-88 came from Ozona.  It'll be an awesome thing to have Bob's old receiver in the shack.  Being only 200 miles from Bob, I was fortunate to be in several round tables with Bob, and have even been to his shack in Ozona, once.

The property we're looking at is probably in the area of around 4 acres.  There are a few land options we're looking at.  With the possibility of property, I'm excited at the aspect of diversity reception.  Having the AR-88 in the rack, along with the three(!) R-274/SX-73 receivers would be awesome! Four receivers, four different antennas, (loop, vertical, inverted V, dipole) a small 4 channel mixer, one speaker - (hopefully) no loss of signal.

Anyway... if anyone reads this thread, again I thank each and every one of you for your comments. 

I'll go along with Jim/W5JO, though... if I can hear 'em, I'll work 'em. 

Seems like S-meters install a 'bias' to the person doing the receiving.

73 = Best Regards,
-Geoff/W5OMR (/5 Spring-ing-ing, Texas)

??IF oscillator??  No such thing in the AR-88.

You should mount that AR-88 mobile and use it with a BC-375.  Now THAT would be a mobile to be proud of ;D

I lived out in Waller, near the Foyt Ranch.

MAN, you can install some ANTENNAS out there in Tejas. 

Here's another little known trick..  When you get out to "ag" (Agriculture) land, 3 phase becomes EASILY attainable.  They  use it to power the pumps and wells for the farms and feedlots in the boonies.  I know of 3 people that have purchased land towards Victoria for the purpose of having 3 phase power to power the transmitters.

You also pay a LOT less for agricultural power.

--Shane

Huge consideration.  I'll be looking into it.  I don't know that I need three phase, though.  I would bring 220v into the rig, and split it off in a breaker panel inside the rack.

Meanwhile, back to the AR-88...

I was at the Rosenburg, TX Hamfest, today.  I picked up another AR-88.  Rough condition, but looks like it'll come back, just fine.  The huge difference in the two is, -this- one has an S-Meter!  For $40, I couldn't turn it down if, for nothing else, it becomes a parts donor for the original W5PYT AR-88.

What I do need to find now, is another bezel for the AR-88 that includes the S-meter opening.  This one, as I said is rough.  On the far left side, something cracked the glass (plastic) and parts and pieces of the glass (plastic) are missing.  There's a hair-line crack near the center window.  The Meter window is fine.

The purist in me says "NO! You can NOT score the 'GOOD' AR-88 glass (plastic) and snap off the meter section and then do the same to the broken piece and then join them together. 

I COULD do that, and then get some chromed strips of metal to go vertically (to hide the seam) between the two horizontal chromed beams.  But I -really- don't wanna come to that.

Does anyone have a junker AR-88 that has a good glass/plastic panel, for band, frequency and S-meter opening?

You might have also noticed, I don't get on here, nearly as much as I used to. 
Please reply via email to my callsign [at] att [dot] net.  Thanks!

-Geoff/W5OMR (/5 Baja Spring, TX)

The plastic window is in two pieces.    The outer window has the cutout for the S-meter; the inner window that reads "RCA AR-88" or whatever can be removed separately.  You need to pull the front panel though.

One sold on ebay recently, here's a pic

(http://i20.ebayimg.com/04/i/001/23/df/8f88_1.JPG)

I just spent an hour searching for another such critter.  Must be like mining for unobtainium.

Should something come up again, please holler quickly!

Email the seller.  I bought two from him about a year ago; he's been selling these about 1 a week lately.

I found an interesting blurb concerning S-meters and AR-88's...

(http://www.qsl.net/w2vtm/Wireless/ar88.jpg)

• RCA's great receiver creation was the AR-88. Designed in 1941, it was a 14 tube superheterodyne with incredible sensitivity (even up to 10 meters), good stability and decent audio (single 6K6.) Much of the production ended up in England or Russia because of WWII. The receiver pictured is actually the last of the '88 versions, the SC-88, (Signal Corps designation R-320/FRC, SN 214), from 1950, which has "band-in-use" masking and the crystal phasing control on the front panel (the AR-88's is internally adjusted.) The AR-88 series' three IF stages are stagger-tuned (with two under-coupled transformers and two over-coupled transformers) requiring a sweep generator and oscilloscope for proper alignment. Many of the AR-88 variations were used in triple diversity receivers like the DR-89 - a seven foot tall rack loaded with three AR-88s and auxiliary equipment. The diversity receivers did not have S-meters installed because the S-meters for all three receivers were actually installed outboard on the Meter Panel of the DR-89 rack. (bold emphasis mine -ge)
  [ http://radioblvd.com/hamgear.htm ]

This tells me that I probably have an AR-88D (I'm ass/u/me'ing the D is for Diversity).

So, the AR-88 'with' a meter is probably just an AR-88?

so far, I know that there's an AR-88, AR-88D, AR-88LF (low frequency). 
Any other info?

--
73 = Best Regards,
-Geoff/W5OMR (/5 Baja Spring, TX)

Yeh, Bob made me jealous.  I never could get my transmissions quite to his degree of buzzardliness.    8)

Geoff - I've seen various types of the diversity model - AR-88, CR-88, etc.  They will have a small knob on the bottom row marked "IF Diversity Gain".  Non-diversity AR-88s won't have this knob.  Don't think the suffix means diversity or not... but I could be wrong.

With a meter......*drool* :P Those meters are scarce as hen's teeth, only Johnny knows where to find them.

IIRC, the 'D' as actually the table model in a cabinet. Plain Jane AR88 signified rack-mount. Somewhere I have the list. Also had an OT tell me that 'A' meant army and 'C' meant civilian, never saw anything anywhere to back that up. I always thought the A meant Amateur since that was where the receivers were intended to go before war broke out.

Weird how they created a new model number for the LF model with the CR91, while the original was simply the AR88LF

They should've been called the HR for Heavy Radio!

Todd said:

Yow! Aint that the truth!  :P

  This AR-88 came from Bob Hohertz, W5PYT. Bob had several, and this one came to him without the two front panel rotary switches, without the wiring harness, and without the crystal phasing IF can. It was a total basket case that he paid top $ for. He was so discusted that he just let me have it so long as I would try to get it going again. He lived long enough to find out that I had it working.

  I actually built a crystal phasing IF can out of a similar vintage IF transformer. Then later Bob found one from a different RCA set (not sure the type). This one had a different IF frequency, but was identical otherwise. It turned out that the only difference was the internal fixed capacitors within across each coil. After switching over to this new IF can, and aligning the crystal filter, it turned out to work the same as my home-made unit. That was a lot of fun going through all of that stuff.

  More recently, this radio as been acquired by Geoff W5OMR who brought it back for a repair. The 6J5 RF oscillator died, and the receiver went dead. I got lucky to just find a bad tube. Once before it did the same thing, and I had to replace a capacitor in the RF cage. It was one of those Mica jobs that is round shaft with a hole in it.

   This radio still could use a complete IF alignment with a sweep generator. I will defer that task to Geoff however..


73,
Jim
WD5JKO

One of these days, Jim.

Are you going to be at Belton in October?

Geoff,

   for almost two months now I work in San Antonio M-F, and then drive back to Round Rock for the weekend. If this keeps up I just might sleep through Belton...

Your AR-88 is ready for you anytime you want to come by.

Not much radio going on with me lately, but I do read AM Fone every day...

Jim,
WD5JKO

That's a habit I'm trying to get back into.

It's been pure hell trying to get caught up ;-)

Been stuck here without wheels (save 2.5 weeks) since the 25th of June.

The 91 Ranger developed a head gasket leak back in Feb (confirmed in early July) wrecked the 06 F-150 in a hydroplaning accident on 25 June, 9 July my 91 CRX was stolen and with it, all my tools and some brackets/bolts for the Ranger that were in the back of the CRX.

That's just -the latest- in the myriad of disasters that's befallen us since we've been here this past -year-.

It's just not been fun here in Houston.

Good news is, I -should- be back in the 06 F-150 this weekend. (Today [Friday], I hope.)

If you don't make Belton, I'll stop by on the way back.  I'll have with me the AR-88 w/meter.  Think I told you I found one of those at a local 'fest for some $40.oo