eHam Forums => Misc => Topic started by: KD2DYY on May 25, 2013, 07:51:48 AM

Title: SWR manual
Post by: KD2DYY on May 25, 2013, 07:51:48 AM
Hey guys. Does anyone out there have a manual OR schematic for an old SWR meter that I just purchased on E-Bay...
It is a Para Dynamics model 3300............. The SWR function seems to be spot-on but my watt meter functionality is all over the place. Any help would be Greatly appreciated......


Title: RE: SWR manual
Post by: K7MH on May 25, 2013, 09:48:54 AM
What do you mean by "all over the place"? Does the meter not stabilize and jump around like a wire is loose? Or you don't get what you would think are accurate wattage readings?
I would not rely to heavily on that wattmeter for accuracy although it may be "ballpark" or relative.
It may be limited in bandwidth, often something like 1.8 to 150MHz and maybe not that high.

To operate it is very similar to most CB SWR bridges.
1. Put it in forward set
2. Key the transmitter and adjust the knob "SWR" to put the meter needle at the "set" mark on the lower scale.
3. Switch to REF to read the SWR or to one of the wattage scales to read the output.

For any change in power level, antenna, or potential for a different SWR you would go through the process again "recalibrating"
it for the change made.

Title: RE: SWR manual
Post by: KD2DYY on May 25, 2013, 11:19:01 AM
No, meter does not jump randomly.... It gives me complete different output on change of bands. At 40m it will show 100 watts. (Kenwood 520s)but on 20 meters it will show 200 watts. (I should be so lucky to get that out of the old boatanchor).
I agree with your comments about the swr use. I am comfortable with the call out on that function with this meter. It agrees with another SWR meter I have so no issues there.It is the RF wattmeter that is in question. I am ready to dive into and scope it out but it sure would be easier with a schematic. Thanks for your help so far.....
I DO appreciate it,.


Title: RE: SWR manual
Post by: KE3WD on May 25, 2013, 11:56:39 AM
Open the meter up and clean and lube its switch contacts with a wee spritz of Deoxit. 

Title: RE: SWR manual
Post by: K7MH on May 25, 2013, 01:29:38 PM
I would try the meter on a dummy load and see what the results are.
I would also take the meter readings from the rig to determine the plate input to the PA tube and compare what they are on 20 and 40.
The TS-520 is about 160 watts DC input on CW and 200 watts PEP input on SSB so you sure are not going to get 200 watts output. I would suspect some other variable we are not aware of is tricking the meter to read high on 20. That is why I would want it on a dummy load and not an antenna that radiates. It may be that the RF field at 20 meters that it is in is strong enough to make it go bonkers.

Title: RE: SWR manual
Post by: KE3WD on May 25, 2013, 03:47:52 PM
Dummy Load testing is good, but do yourself the favor and clean those controls first. 

Title: RE: SWR manual
Post by: KD2DYY on May 25, 2013, 07:25:04 PM
Thanks to all. I have not tried the contact cleaner. I will get to that in the morning. Like the nice big meter on the rig and I will keep trying to get her to tell me correct output... Guess there were not to many of those meters sold. Oh well.
Thanks to all for the help. Still looking for schematic .


Ps 40 was very noisy tonight. I tried but no good with barefoot. I just got a SB200 today and will get that running ASAP.

Title: RE: SWR manual
Post by: K8AXW on May 25, 2013, 08:09:29 PM
It's been my experience that CB SWR meters are very frequency sensitive on the power scale.  The SWR section should be OK on HF though.  The contact cleaning certainly won't hurt anything but to make a 100w difference..... I don't think so.

Title: RE: SWR manual
Post by: KE3WD on May 26, 2013, 06:44:39 AM
Depending on the design and component choices, of course, I have indeed seen quite a few of the "CB" power/swr meters with dirty or dry contacts in my experience. 

Some of them were at levels much higher than the 100-200W as well, with readings all over the place. 

If the meter is using diodes and their associated voltage drops, which can be rather low in voltage indeed, the resistance of a dry or dirty switch contact can really change the readings on the things. 

It has been my experience over the years that quite a lot of used gear acquisitions are indeed in need of the sprayout of controls with the Good Stuff. 

Have personally observed many a piece of nonworking or partially working gear come immediately back to life from the simple clean and lube of all controls. 

Another thing noticed over the years - quite often is the case that the used rig or other device is not really out of calibration or alignment at all, just the added bad connections and higher resistances of those critical switch contacts are throwing the unit's original alignments off. 

After clean and lube, mechanical operation of the controls essential while still wetted, I've seen many an old box slide right back into factory cal and alignment.  Or darn close to it. 

Ole Ben Franklin informed us that Cleanliness is next to Godliness...

And manmade stuff does not heal all by itself. 

The ehams can do what they like, or not do it, but as for me, I shall continue to pull the covers off of every "new" used acquisition here, visually inspect, tighten screws that may be grounds, apply Deoxit to the controls, at a minimum before placing the device into permanent place in the shack.   

Of course, that does not imply that I don't first do a setup and turn-on on my testbench in order to observe what I've got first.  And if all the controls seem to be already working, lubed and operation looks okay, then of course there is no need - yet - to waste my Deoxit on the piece. 


Title: RE: SWR manual
Post by: KD2DYY on May 28, 2013, 04:42:59 PM
Thanks to all who have generously giving time to write me on this issue....I will clean all switches and contacts.
It is not an expensive meter but If I can get it to "settle" it should do fine for me in the short run.... I am working on an old SB200 right now and I really wanted to check out the power output of the amp. before I attempt QSO's. Whew.....
I tried to get on this site last night but the "server" must have been out to lunch.
Thanks ,again, ALL and best of 73's.

                                                                                                      KD2DYY Formally (WA2AMZ)

Title: RE: SWR manual
Post by: W4KVW on June 01, 2013, 09:58:50 PM
I don't think this meter is designed for any bands other than maybe 10 & 11 meters? I could not find the manual on line but most all of them are designed for 25 to 30 mhz ONLY as I recall & that could be a BIG part of the problem.  ???