Looking for a 75MHz Frequency Checker?

[Rick_TYler]

This is not an endorsement, an advertisement, or an official message from IFI, but I just bought two of these for our robotics club’s use. It’s a frequency checker which scans the 90 channels in the 75MHz range, and is an easy way to look for interference on VEX channels. This is the unit that John V-N recommended for testing, and I found it on sale at Tower Hobbies online for $4.99. That’s “four dollars and ninety-nine cents” in case you thought that was a typo: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJUP3&P=7.

I don’t know why they are selling it so cheaply, but – like I said – I just bought two.

[bellpride]

Thanks for posting - it’s the perfect thing for our tournament. Now we can check it if teams complain of interference, and it would be great for patrolling the pits too.

[fryfrog]

Thanks, I ordered one of these also. They have a link to one that checks the 72MHz range and it is $30 more expensive.

[lyncas]

I just purchased two, thanks for the great find Rick !

I’m considering bringing them to other people’s VEX events to verify they are watching their frequencies !

[Quazar]

Mine just arrived, and it seems to work well. I tried it with a couple transmitters on different channels and it spotted them both, as you would expect.

I wanted to post a couple details from the instruction sheet to help folks who are thinking about getting it. (These are also mentioned on the Tower Hobbies page that Rick provided a link for, but I wanted to point them out as particularly relevant):

It’s important to note that the Frequency Checker is NOT well suited to show very brief, intermittent Rf signals that could cause interference which may be present in the environment near or between R/C channels.

This is because the frequency checker is a scanner - it scans through all the channels every 10s or so. This means that it is watching each channel for about a third of a second every ten seconds. If the interference doesn’t hit at exactly the right time, the scanner won’t see it.

INDOOR RACE TRACKS

When used inside enclosed buildings, particularly those constructed with a steel structure covered with a metallic surface, it’s possible that the Frequency Checker might show some erratic behavior. Such facilities can cause excessive reflection of Rf signals, and might cause the Frequency Checker to indicate that some frequencies are being used when, in fact, they might not be. This condition will typically worsen as more transmitters are in use.

This sounds like it might be relevant if you want to use the frequency checker at a competition.

Still, hard to beat the value at $5!

Cheers,

• Dean

[Foster]

I picked up 4 for our events here. Does anybody know about the need for an external antenna?

Foster

[Quazar]

@Foster

Does anybody know about the need for an external antenna?

It just extends its range.

The description on the Tower Hobbies page says that the range is up to 300’ with the built-in antenna and up to 1000’ with the optional external one.

It also says that using the external antenna might make it more sensitive to reflections if used inside a structure with lots of metal.

Cheers,

• Dean

[MarkO]

@Quazar

Mine just arrived, and it seems to work well. I tried it with a couple transmitters on different channels and it spotted them both, as you would expect.

I wanted to post a couple details from the instruction sheet to help folks who are thinking about getting it. (These are also mentioned on the Tower Hobbies page that Rick provided a link for, but I wanted to point them out as particularly relevant):

This is because the frequency checker is a scanner - it scans through all the channels every 10s or so. This means that it is watching each channel for about a third of a second every ten seconds. If the interference doesn’t hit at exactly the right time, the scanner won’t see it.

This sounds like it might be relevant if you want to use the frequency checker at a competition.

Still, hard to beat the value at $5!

Cheers,

• Dean

For a $5.00 Item, it might be worthwhile to see if the Scanner Circuit can be modified to scan a Sub Range, or even pause on a Given frequency, or it potential Harmonics Frequencies.