vlf transmiter, need more range

External antenna. It's on their web page:

If you have a larger than average yard, consider purchasing an extra boundary kit. The boundary kit includes additional wire and flags.

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consider purchasing an extra

There is no wire in this kit, it's wireless.

The manufacturer sells an additional transmitter, which is very expensive.

My question was regarding methods for hopping up the transmitter or adding a better (external) antenna.

Can you help?

Thanks

Al.

Increasing the transmitter power significantly or adding an external antenna would violate Part 15 rules and also invalidate the FCC type acceptance. Having said that, here's the transmitter schematic.

OK, thanks very much Travis.

It appears easy to modify or to bulid another unit, reproducing the coil is probably the toughest part.

I'm not familiar with the ic's, but should be able to locate data for them.

I'm really quite surprised to find that there is not a single transistor oscillator, but that sure looks like the beast!

I don't think there is a part 15 regulation for 17 khz. because it's almost audio frequency. If there was a part 15 for frequencies that low, they would have to type accept every audio amp that has a transormer or coil associated with the output, wouldn't they?

I can't imagine 17 khz going very far, especailly since the 'antenna' is so short relative to the carier frequency.

I do thank you very much for the help and wish you the best.

Al

The U.S. RF spectrum allocation starts at 9.0khz and unlicensed devices must conform to Part 15.

9.0 to 14.0khz is allocated for radio navigation use (in the U.S. the now mostly obsolete Omega system was the largest user of this spectrum).

Are you sure the transmitter actually uses such low "carrier" frequency? I have not looked a the schematic that was posted, but I don't see how this could actually work at that frequency since as you yourself admit, this is in the high audible freq. range.

I would think that the collar based receiver might emit the 17Khz tone when the animal wearing it strays beyond the RF transmitter's range. I would think though that the transmitter itself would use an approved FCC RF frequency in the Mhz or low Ghz range.

Bob

It is magic.

Hi Bob,

The 17 khz frequency sounds a little odd to me also. But, there is some literature on the website that indicates that's the frequency of the transmitter.

I have a few ideas regarding WHY they use such a low frequency...........

First, they probably have experience at vlf. There are other models that use buried wire to define the dogs limits in travel. You can bury an antenna at these lower frequencies, which is why they are used for navigation and communication with submerged submarines.

But, obviously, the range has to be very limited because the thing doesn't have an external antenna. Even if it did, the antenna would be a poor radiator because the antenna is so short relative to the wavelength.

Also, direct conversion receivers at these low frequencies are very easy to build, a single transistor and a diode detector is easy to build and cheap.

If I was designing the thing, I'd use 433 Mhz, where simple and low cost data receiver and transmitter chips are available and do not use much power from the battery.

Check out the schematic, there are 3 chips that feed different windings on a transformer and the time constants in the schematic don't make sense for transmitters in the MHZ and higher range.

Regards,

Al

OK, thanks Travis, I learned something new!

Regards,

Al

Actually, the fundamental emission frequency is 18.7khz.

fcc_id='KE3IF100'

It has a 32.76 Khz crystal, wouldn't the transmit frequency be around

16.3 khz?

Does anyone know the identity of the single chip that has 32 pins and appears to drive each of the LM1875T transmiter chips? I can't make it out on the pdf I downloaded.

Thanks,

A

The ASIC is likely a PLL synthesizer, so the output frequency isn't necessarily an even multiple of the MO frequency.

The ASIC is a 'black box' and we can't really determine the rf output frequency by looking at the chip itself.

However, the 3 driver chips are 20 watt AF amplifiers. That tells us that hte output has to be less than 20 Khz.

The wall wart looks physically small, so it's a reasonable to assume the output power does not come anywhere near 60 watts...

I looked the pictures on the fcc website and I see that the coils are not in a transformer configuration....they appear to be one coil for E-W vertical polarization, one coil for N/S vertical polarization and the third chip drives the coil for omnidirectional horizontal polarization.

Since the chips aren't on a very large heatsink, it is probably possible to easily increase the output by properly heat sinking the drivers and by increasing the drive to each amp stage (after checking part 15 rules and regulations).

My guess is that the coils will easily withstand the additional output power.

Once again, I say thanmks to all who commented and helped me figure out what was inside that unit.

Regards,

A

Hi Travis,

I hope you will see this, not sure how often you monitor this NG.

I have searched the FCC part 15 document looking for antenna and power limits at 17 KHz. But, I can't find anything.

Do you have any more information?

Also, are you able to find any information on the Radio Systems PIF-275, which is a receiver for the IF-100 transmitter you helped me out with previously.

Thanks,

A

The emission limits are included in the test documents. As I recall the fundamental emission as tested was about 25 uV/meter below the limit at

300 meters.

I didn't look for information on the receiver, but if you can determine the type acceptance number you can look it up on the FCC web site --

Thjanks Travis.

I'm into the search url now, they have 22 products registered (KE3) prefix. I'll search them all as the summary doesn't describe the product very well.

GL.

A