Hobbico Frequency Checker Incorporated Into a Frequency Board

[Miami Mike]

Paul Emerson of the RCSE list thought of this before I did, and I think it's a great idea. I intend to try it just as soon as I can get one of the new Hobbico 72MHz Radio Frequency Checkers (http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJUP2&P=7
) that Tower Hobbies expects to have some time in May, 2005. The idea is to take one apart and incorporate it into a frequency board so that each channel slot has its own LED indicator.

If others here are interested, we can swap some ideas while we're waiting for the units to become available.

[fhhuber506771]

My first idea is... I would EXPECT to need some form of circuitry addition to drive the (adviseable) larger, brighter LED's on the board using the output INTENDED to light the LED's in the device to trigger the higher power LED circuits.

(I don't think a palm sized device made for one guy to look at it will drive LED's large enough to see from 5 ft. its 3.14 X 2.36 inches... about the size of the Hobbico Tachometer.)

[Miami Mike]

I'll bet the LED array is wired in a matrix of 8 rows and 7 columns, or vice versa, and the LEDs are strobed. If so, there will be one eight-bit strobe output chip and one eight-bit return chip. Buffering those two devices should enable driving brighter LEDs.

[lazy-b]

Guys: been thinking of making one, but I guess, its cheaper just buy a Ready-made unit,as posted by miami mike. plan to use a synthesize receiver and hack it as a SCANNER.

Still waiting for ezoner here, to send me his proto-type synthesize receiver, I can use a another pic-chip to interface thru a channel selector, and automatically scan the whole 72MHZ, and can make a LED indicator to give active channel.

Saw a Futaba RC Monitor, but its really expensive.

[Norman Adlam]

Hi,

I'd be interested in anything similar for 35MHz!

Cheers

[fhhuber506771]

Hi,

I'd be interested in anything similar for 35MHz!

Cheers

My bet is... if you contacted Hobbico they could make one. (probably not as inexpensive due to the modifications... )

[Miami Mike]

I doubt it. You can see in the picture that the unit is made in Korea, so they'd have to special order it. The rf section would be different because of the difference between 35 MHz and 72 MHz, and it would have to scan 36 channels 10 KHz apart (http://www.ukrcc.org/35mhz.html) instead of 50 channels 20 KHz apart (http://www.modelaircraft.org/Comp/frequency.htm). It would make more sense to copy some of the ideas they used and build one from scratch.

Now if this unit sells well and someone decides that a sufficient demand exists for a 35 MHz version, you might see one some day.

[Miami Mike]

They're being shipped now, I just got notice that mine is on the way. The first step in this project will be to determine if it's feasible to build an interface.

[KillerWatt]

Hi Miami Mike.........sorry 'bout the "Radios" postings thing.....Anyhow, the Hobbico appears to be preety good quality, all SMD type constructed with a 5 verticle X 10 horz seperate Led matrix display, good chances of extending the Led drivers to signal a seperate display of any size....Display cycle starts in upper left (chan 11) and scans (lites-up indivually) each chan frequency Led at about 3 chans per second rate, scanning left to right, then dropping to next lower horiz row and repeating scaning left to right until chan 60 is reached....Only the active freq chan(s), (when scanned), Led stays "on" until the scan restarts at upper left (chan 11).....From the "Radio" post, do you have any ideas about what i'm probably hearing with audio sniffer ??....Sounds like normal FM receiver signal "most quieting with strongest carrier" but without any demodulated audio heard on both the wide area "mystery" chans 24 and 25 and my RC Fm Tx....... Do you think a seperate demodulator is needed to hear either the probable pager Tx and my RC Tx's pulse rate ??....... kw

[Miami Mike]

Thanks for the description, I think I get it now. Apparently if there's a signal on channel 11 and another on channel 60, the 11 LED will stay on during the entire remainder of the scan, while the 60 LED will turn back off almost immediately after it lights. I would have expected that any of the 50 LEDs would remain lit until reached again in the scan, but I guess not. I assume there's an extra pause after the 60 LED lights and before the scan restarts, to give you a chance to see it before it turns back off.

Here's a link to your question in the Radios forum for anyone else who's interested:

http://www.rcgroups.com/forums/showthread.php?p=3786077&postcount=30

Since the first step to any modification of the Hobbico Frequency Checker will be to figure out how it works, maybe we'll both get some help here in figuring that out.

I hope to get mine tomorrow.

[KillerWatt]

Mike.....Any and all of the "active-when-scanned" chan Led's will stay "On" until the display scan reaches chan 60 (the last Led, bottom row,far right), then the only "still active when re-scanned" chan Led will stay "On" while the others go "Off" when they are re-scanned....so a carrier could come on and go off while not being scanned at that exact time and NOT be picked-up and lit...but once lit, will stay on (even if the carrier has now gone off) until re-scanned and the carrier not on at exact time of scan........harder to explain than to use, but i've only had mine for a day or so....... kw

[Miami Mike]

I finally got mine today. Here's how it scans:

There's nothing special about channel 60, and nothing special happens to the other LEDs when the scan restarts at channel 11. Any of the 50 LEDs that stay lit after they're scanned will continue to stay lit until they're reached again in the scan, at which point they'll either go off or remain on. It's the way I expected it to work, but I understand that it can be hard to explain.

I built an antenna for mine this evening. I posted some pictures and details in the other thread in the Radios forum here (http://www.rcgroups.com/forums/showthread.php?p=3797447&postcount=40).

I opened it and looked it over. The smaller board is the receiver and the larger board is a PIC microcontroller-driven LED matrix, which consists of ten strobed columns, each with a transistor delivering a negative pulse in sequence, and five return rows, each with a transistor and series 33 ohm resistor to provide the positive return path for that row.

The unit has a seven inch long internal antenna wire that wraps around the inside of the case and terminates at the ground connection of the antenna jack. The tip and side connections of the jack don't connect to anything. When an external antenna is plugged in, it becomes an extension of the internal antenna.

I believe a circuit could be built to drive larger and brighter LEDs from this unit, and it could even be interfaced to another microcontroller for added features such as showing the recent activity history of each channel. But before I modify it I want to get an idea of how well it works. So far it seems to give a lot of false indications with no r/c radios around, but I still haven't seen how it performs at an actual flying field.

http://www.vvsss.com/freq_checker/both_boards.jpg

[DDwaneR]

I ordered 2 of the units from Tower. Both of the units don't false ID without a external antenna. Both display accurate information even with a transmitter within 12 inches and other transmitters beyond on different channels. If a long external antenna and 2 or more carriers are generated within about 100 feet, spurious indications start however.

[Hennisdk]

Is there any chance that someone will build one from scratch?

Here in South Africa we have 35 MHZ,53MHZ,54MHZ for planes and Heli's and 27MHZ for Cars. The other problem is, we had 25 channels for 35MHZ, and I checked the available scanners and they support the 25 channels but we have 50 channels for 35MHZ just for South Africa NOW. I contacted them and they said there is no chance that they are going to upgrade their units for the NEW South African channels. That is why I was hopeing that someone has developed their own Frequency scanner so that I can maybe build my own that can scan all the extra channels including 53MHZ, 54MHZ, 27MHZ.

Thanks for your undevided attention :)

Hennis de Klerk

[KillerWatt]

I accidently posted a question about the Hobbico Scanner in the wrong (Radios) topic area.....Looking for help in adding a few mods to manually stopping the "scan" on a channel and adding an "audio demod out" for being able to monitor and listen to the unidentified active channel for things like a standard RC Tx pulse train or actual pager voice modulation......could make I D ing the unknown Tx easier...Any ideas on how to do this to the Hobbico init.....kw