-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Equiping a test/repair bench
- Thread starter mb91w126
- Start date
A decent freq counter will have a TCXO ('temperature controlled crystal oscillator' pictured above) in it. That will keep it pretty stable after it warms up. W/o a TCXO, it won't get stable and be reliable when adjusting radios. The TCXO is differrent from just a regular crystal in that it has its own heat source so that it can reach its assigned freq and stay very stable there. W/o a heating element, a crystal can/will drift.
I don't know if your counter has one.
I find it hard to accept that your counter can read down to 1hz since there are only six places that it can read out - unless it eliminates the Mhz places altogether. The Hp 5316A counter I use can read 27.000.000mhz (an example); that takes up eight readout places. Your counter only has six places that readout. The last two places being the most significant when doing alignments.
Look at the face of your counter. You can count only six places on it; so how can it read an eight digit number? ANS: it can't. Hope this point makes it clear now.
Sure hope your counter can do that.
Last edited:
Well I bought it and I am gonna use it......if I can find the proper probes.
It has 2 settings 1 second and auto?
Its solid built.
Last edited:
A decent freq counter will have a TCXO ('temperature controlled crystal oscillator' pictured above) in it. That will keep it pretty stable after it warms up. W/o a TCXO, it won't get stable and be reliable when adjusting radios. The TCXO is differrent from just a regular crystal in that it has its own heat source so that it can reach its assigned freq and stay very stable there. W/o a heating element, a crystal can/will drift.
I don't know if your counter has one.
I find it hard to accept that your counter can read down to 1hz since there are only six places that it can read out - unless it eliminates the Mhz places altogether. The Hp 5316A counter I use can read 27.000.000mhz (an example); that takes up eight readout places. Your counter only has six places that readout. The last two places being the most significant when doing alignments.
Look at the face of your counter. You can count only six places on it; so how can it read an eight digit number? ANS: it can't. Hope this point makes it clear now.
Sure hope your counter can do that.
Yes...I understand....but I cannot afford a piece of lab equipment like that...have to do the best I can with what I can afford.....sorry I did not post sooner...but I missed your post....thanks for taking the time to get your point across.
Here is the probe BK designed for the 1801.....I need to find one or its equivalent.
Direct and 10:1 test Probe PR-25 Equipment B&K Precision
Direct and 10:1 test Probe PR-25 Equipment B&K Precision
Thank Rob and all
I'm getting there, I did my homework and now understand the difference between a frequency display and a frequency counter.
So we need
DVM and analog meter
Frequency counter
Watt meter
Bench radio
Service informantion
If we could continue, next is the signal generator, an RF signal generator. From what I read I need something to inject a tone into the radio, Rob I saw your article on using a radio as one, very nice. Am I correct in assuming that I will need something in the 1-30Mz range with adjustable output level?
1. Any recomendation?
2. Then won't I need to build a RF probe to "see/hear" the signal?
Understanding that this is without using a computer or scope.
I'm getting there, I did my homework and now understand the difference between a frequency display and a frequency counter.
So we need
DVM and analog meter
Frequency counter
Watt meter
Bench radio
Service informantion
If we could continue, next is the signal generator, an RF signal generator. From what I read I need something to inject a tone into the radio, Rob I saw your article on using a radio as one, very nice. Am I correct in assuming that I will need something in the 1-30Mz range with adjustable output level?
1. Any recomendation?
2. Then won't I need to build a RF probe to "see/hear" the signal?
Understanding that this is without using a computer or scope.
Much easier to build that to buy. Commercially made samplers are just ridiculous in price and frankly just aren't worth it or even needed for your needs.
Requires two female SO-239 connectors, one female BNC connector, small project box (you might even use an Altoids box), one ferrite sleeve, a 100 ohm/1/4 watt resistor, and some scrap wire. You don't have to be a rocket scientist to do this project; probably take you more time to drill the holes for the BNC/SO-239 connectors than it would to put it all together - honestly.
This is no a complex circuit here, a monkey could build this. Don't be afraid to try.
Not to the sig gen; it goes to the input of the freq counter. That ferrite bead in the previous photo is picking up the radio's signal through the wire by induction. There is no direct contact, it is all done by/through inductive sensing of the RF output.
For example, you can take a piece of ordinary wire and wrap it a 5-6 times around you coax and connect those wire ends to a freq counter and it will be able to pick up enough signal to read the transmitted freq through induction. All this RF sampler does is pretty much the same thing, except that it is in a shielded metal box and it uses a piece of ferrite to accomplish the same thing a little better/neater. A resistor is put in series with this wire so that it can be used if more than 50w is being transmitted. Having connectors on the box make it easier to hook things together with cabling - is all . . .
Last edited:
Not a dumb question.
But no; it needs to have wire wrapped around the ferrite 5-6 times so it can pick up a very slight voltage that can be read by the freq counter. WE only need enough of this to 'trigger' the freq counter.
When transmitting, your coax will have an electromagnetic field around it. If we wrap just 5-6 turns around the coax, the wire is now inside this electromagnetic field and enough of those electrons get trapped in that wire. They will oscillate at the same freq that is being transmitted through the coax. Just a very small amount is being drawn away and not anywhere near enough to affect radio output; so not to worry. But it is enough so that the freq counter can sense it and read it. However, if you run 1,000 watts through that coax, that voltage can be considerably higher. So, a resistor is used so that too much voltage is kept out of the freq counter; or it could burn out the counter. You don't need to test freq at high power levels anyway if you are aligning a radio; this is used for testing and adjustments.
Last edited:
Sure, but it would be a mess when you are trying to align a radio. You need it to be consistent and stable so that your readings can be dependable enough that adjustments can be made if necessary.
BTW - That RF sampler can also be connected to an O'scope instead of the freq counter and the transmit waveform can be seen this way. I use the sampler for that - too. Seeing the waveform can give you the means to adjust AM modulation so it can be set at 100% properly. Superior to using a modulation meter - which are never accurate enough.
Last edited: