Signal Monitor Scope and Panadapter experience/advice

[David, K3TUE]

FLUFF:

I have acquired a shack receiver finally for my AM station.  I decided on a Drake R-8B as my best compromise between size, weight, sound, modernity, potential for longevity, sensativity, selectivity options, and potential for interesting mod ideas.

I am looking into transmitters right now, and seem to be settling in on a late model Johnson Ranger (I).  That's the one with the extra keying tubes behind the panel ot the left of the VFO knob, right?  It seems like a good jumping off point and is tube to boot to offset my solid-state choice of receiver.

What I am looking for though, is advice on some of the support items for this setup.  I am planning on foregoing an amp for now, pending a power upgrade to the shack.  I am already on my way looking at a microphone.  But there seems to be two mroe items that have cought my eye.

MEAT:

I am looking for insight and advice on the following stations accessories:

TX RF signal monitor scope: the Heathkit SB-610 seems to be a easy/logical choice.

RX IF panadapter band scope: the Heathkit SB-620 seems to be an equally easy/logical choice.

What I would like to know is, are they worth the purchase?  Or would the smarter/more generic idea be to use an oscilloscope?

I believe that using a 'scope is relative trivia as an TX RF signal monitor.  Or am I wrong?

I also believe that using a 'scope is trickier as an RX IF band scope, requiring a sweep circuit (perhaps an interesting project) to convert from time to frequency domain.

From what I understand, a TX RF signal monitor is all but required to put out a clean AM signal, but the RX IF band scope is more simply a handy convenience.  And since an oscilloscope is a very usefu piece of test equipment, I suspect that going the more generic 'scope route might be a better investment.

Opinions?

[WA1GFZ]

Consider a clean HP141 spectrum analyzer for a monitor. It is calibrated
and a useful tool in the shack. I found the 620 a toy that isn't very useful.

[WV Hoopie]

Hi Dave,

Another option might be a cheap $25 hamfest o'scope. For watching a waveform or trapezoidal pattern a 5 MHz cheapy will do the trick. Some of the older (1960's) A double R L handbooks give examples of how to build a RF pick-up coil and the circuit for watching a trapezoidal pattern. If you are interested, I might be able to scan some of my good old Angel Music stuff. PM if interested, I'll try to be of some assistance.

PS: Good test equipment and their uses, which ones to purchase and why would be a good addition to the AM Online Handbook.

Hoopie,

[WA1HZK]

Around here we take a used dual trace scope & feed the top trace into the rcvr. and the bottom trace into the transmitter. Good for telling when Brent is fired up.
Keith
WA1HZK

[KA8WTK]

The SB-610..... I have one of these in my SSB station. Works ok fine.
The SB-620......I have one of these also. The ONLY reason I have it is to complete the SB401/301 station. Otherwise, nice toy but no real practical use I have put it to. Looks nice when on.
HO-10.............Usually cheaper than a SB-610 and does the same thing. Have one in line for the AM stations.
Ham-Scan.......Works like the SB-620, usually cheaper. It is interesting to watch the effect of the R-390A filters when you crank them in, but otherwise just nice to look at.

The Hamfest Scope Cheapie.....Here is the cost effective choice for monitoring your transmitted signal. The dual trace idea above is quite good.

Goto to the AMFONE page and then to East Coast Sound. Look at K1JJ's scope pickup (left hand side of page) for a way to hook up the Hamfest Scope.

[Pete, WA2CWA]

SB-620 panadapter won't work with the Drake R8B. First !F of the R8B, where you would connect (at the input of the IF) the SB-620 is 45 MHz. The 620 is designed to work with IF's from roughly 250 Hz to about 4 MHz depending on the 620's input LC network. To make the 620 work with the R8B, you would have to design a mixer interface to mix down the 45 MHz signals into a range that the 620 can see.

[WA1GFZ]

I have mine on the second IF before of the filters on the TR7A 5.645 MHz

[w1guh]

All suggestions are good and easily workable.

Given that a decent (not necessairly expensive) lab scope is a good piece of test equipment to have in the shack, and if you only want to have one scope, that plus a pickup (for transmitted RF "any ol' thing'll" work.  Just the probe itself close to the final amp will pick up more than enough signal to monitor the waveform.

But to me, the ideal solution is the above for troubleshooting/analysis and for looking at the received waveform (that can be tricky depending on the rx characteristics) plus a Heathkit monitor scope for keeping an eye on your transmitted signal.  What it's got going for it is ease of hook-up and operation.  It hooks into the coax out of your transmitter just like an SWR bridge, and has controls to keep the waveform the right size.  Plus, it's got switching for envelope and trapezoidal patterns.  If you're ever planning runing AM linear, it's almost imposible to tune up w/o a scope.  Same thing for screen modulation.  The minus is that it really can't be used as a lab scope at all, it's strictly a signal monitor.  But, IMHO, since AM operation really needs a full-time tube for monitoring your signal, if you've got two scopes, you're golden.

I've used both the SB-610 and the older HO-something or other.  They're functionally equivalent.  Guess the difference is if you want it to match a Scratchy Apache.

Have fun on AM!

Paul

[w3jn]

Forget the Heathkit monitor scopes.  They're somewhat problematic, they're not very sensitive, and they're one-trick ponies.

You can nab a decent scope at any hamfest starting at $5.  $50 should get you a 50 MHz dual trace triggered sweep job.  

Not only can you monitor your xmitted signal as well as the receiver IF you can do troubleshooting with something like this as well.  And they're sensitive enough you don't need a direct tap to the RF line to get a trace.

I have 6 scopes kicking around and wouldnt get on the air without one nor would I try and do serious troubleshooting without one.

Try to get a Tektronix if possible but lower end ones such as B&K, Panasonic, Mitsui, etc. work OK as well.  HP scopes have a tendency to have dirty switches and other problems.  Although they're a great deal if you find one with just dirty switches - I scored a 400 MHz dual trace HP scope for $20 - all it needed was a good douching of the controls and switches.

73 John

[W3SLK]

I just picked myself up a perfect OS-8 for $20. Came with the cover, probes and an original manual!

[David, K3TUE]

AFAIK, the SB-620 could be used with the R-8B along with a Sherwood MIX-3 to make it 455kHz.