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Versatile C. Crane FM Very Low Power Transmitter

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Kennelly Heaviside
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Versatile C. Crane FM Very Low Power Transmitter

Post by Kennelly Heaviside » Thu Nov 18, 2021 9:21 am

Anyone have any experience with this particular device? I've always been very disappointed with the range of such devices. This one has the advantage of using "in between" frequencies to help with interference. It also has a simple monitor to avoid overmodulation. With Tom Kneitel One Transistor transmitters, back in the day, I used a Panasonic Clock Radio with a narrow IF Filter and backed the volume down until there was no distortion.

The Part 15 legal inverse field limit is extremely low, making most similar devices virtually useless in my experience.

https://www.youtube.com/watch?v=ufb2L_Bay8g

Manual.

https://www.solidsignal.com/Manuals/FM2.pdf


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Turkeytop
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Turkeytop » Thu Nov 18, 2021 2:48 pm

I have it. With the illegal modification I made to it it works great. In the user manual they spell out exactly the adjustment you mustn't do that makes it illegal. They even show you in a diagram what it is you aren't allowed to do.

I have a SXM receiver in the house I feed into the C Crane xmtr. I can pick up the signal anywhere in the house or in my yard. On the car radio, it's good up to about a half block away.


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k8jd
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by k8jd » Thu Nov 18, 2021 3:05 pm

Transmitting on "between channel " freqs does not help much because most good receivers, today, are locked down digital tuners.

The only thing I know about poor range is hardly anyone who messes with those transmitters had no clue on antenna theory or construction !
Running a piece of wire out the window may not get you range you expected.
What have you been using for an antenna there ??



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Turkeytop
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Turkeytop » Thu Nov 18, 2021 3:18 pm

I don't have a whole lot of knowledge either. I just did what they told me not to not to do. It didn't modify the output frequency in any way. There are plenty of unused frequencies in this area. I selected 90.1 MHZ

The illegal modification actually boosts the output power very noticeably.

I just now took a look at the manual the OP put up. I see it no longer shows what not to do. I'll open mine up and post a photo.


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Rick Grenon
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Rick Grenon » Thu Nov 18, 2021 3:37 pm

I had one in the 90’s, a friend modified mine to get about half a mile. I hooked up a CD player and had a small pirate station. Those were the days. I also remember the Talking House transmitter for above AM 1600, those were great for transmitting illegally too.
Last edited by Rick Grenon on Thu Nov 18, 2021 4:01 pm, edited 1 time in total.


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Turkeytop
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Turkeytop » Thu Nov 18, 2021 4:01 pm

Here's the mod.

On the back of the board is a variable resistor, VR2. I've indicated it with a red arrow. It used to say in the manual, not to adjust it fully clockwise. Or it might have been fully counter clockwise. I forget which. Just experiment with it.

Image


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bmw
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by bmw » Sat Nov 20, 2021 11:42 pm

I have one (version 2). Stock, it barely got me a reliable signal 15 feet away across a room. Make that mod, and instantly I had entire house and yard with no coverage gaps at all.

Taken even a step further, swap out that puny antenna with a larger telescoping antenna and adjust your length to exactly 1/4 wavelength for whatever frequency you're broadcasting on and you can get up to 3/4 of a mile in a car. And I did confirm that being close to that 1/4 wavelength made a big difference in range. Not bad for a pair of AA batteries.

Sound quality on these is very good as well.



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Turkeytop
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Turkeytop » Sat Nov 20, 2021 11:52 pm

Thanks for that tip. I tried lengthening the antenna on mine, but only by clipping a random length of wire to it. That didn't help much.


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Rich F.
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Rich F. » Sun Nov 21, 2021 6:54 am

As a "heads up," the FCC is quite active at finding and issuing citations to unlicensed users of the FM broadcast band that do not meet their Rules. Below is a sanitized example of this ...


FEDERAL COMMUNICATIONS COMMISSION

ENFORCEMENT BUREAU
Northeast Region

New York Office
201 Varick Street
New York, NY 10014

NOTICE OF UNLICENSED OPERATION

Case Number: XXX
Document Number: XXX

The New York Office received information that an unlicensed
broadcast radio station on XXX MHz was allegedly operating in
XXX, NY. On XXX, an agent from this
office confirmed by direction finding techniques that radio
signals on frequency XXX MHz were emanating from your property
in XXX, NY. The Commission's records show that no
license was issued for operation of a broadcast station at this
location on XXX MHz in XXX, NY.

Radio stations must be licensed by the FCC pursuant to 47 U.S.C.
§ 301. The only exception to this licensing requirement is for
certain transmitters using or operating at a power level that
complies with the standards established in Part 15 of the
Commission's rules, 47 C.F.R. §§ 15.1 et seq. Your operation on
frequency XXX MHz was measured at 392 microvolts per meter
(µV/m) at 483 meters. This exceeds the allowable unlicensed
limit of 250 microvolts per meter (µV/m) at 3 meters established
in Part 15. Thus, this station is operating in violation of 47
U.S.C. § 301.

You are hereby warned that operation of radio transmitting
equipment without a valid radio station authorization constitutes
a violation of the Federal laws cited above and could subject the
owner of this illegal operation to severe penalties, including,
but not limited to, substantial monetary fines, in rem arrest
action against the offending radio equipment, and criminal
sanctions including imprisonment. (see 47 U.S.C. §§ 401, 501,
503 and 510).

UNLICENSED OPERATION OF THIS RADIO STATION MUST BE DISCONTINUED
IMMEDIATELY.

You have ten (10) days from the date of this notice to respond
with any evidence that you have authority to operate granted by
the FCC. Your response should be sent to the address in the
letterhead and reference the listed case and document number.
Under the Privacy Act of 1974, 5 U.S.C. § 552a(e)(3), we are
informing you that the Commission's staff will use all relevant
material information before it to determine what, if any,
enforcement action is required to ensure your compliance with FCC
Rules. This will include any information that you disclose in
your reply.

You may contact this office if you have any questions.

Daniel W., Noel
District Director
New York Office

Attachments:
Excerpts from the Communications Act of 1934, As Amended
Enforcement Bureau, "Inspection Fact Sheet", July 2003



Deleted User 14896

Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Deleted User 14896 » Sun Nov 21, 2021 7:44 am

Rich F. wrote:
Sun Nov 21, 2021 6:54 am
As a "heads up," the FCC is quite active at finding and issuing citations to unlicensed users of the FM broadcast band that do not meet their Rules ...
I may be incorrect. But I'm fairly confident the FCC and CRTC are not concerned with any of the modifications we've seen in this thread so far. No one is feeding 100 watts into a collinear on top of a building or tower.



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Ben Zonia
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Ben Zonia » Sun Nov 21, 2021 8:26 am

It's kind of interesting if the FCC were actually be going after "optimized" Part 15 type transmitters, though.

The FCC recently came up with a whole new set of rules regarding interference from legally authorized translators with an ERP of 250 watts maximum, to licensed stations within their 45 dBu contours, well below any protected 54, 57, or 60 dBu contour. The complaint must come directly from broadcasters, not directly affected listeners, and there must be a certain number of complaints meticulously documented. This is being used to capriciously harass licensed translator operators. WKAR (AM) has already been forced to change its frequency twice due to complaints from big group owners.

In some cases, a Class A STATION would be allowed nearby on the same frequency and not be able to be bumped, but a translator could be.

I agree, FM stations do provide useable service at the 45 dBu contour and even lower in many instances. And it irks me no end how trasnslators are authorized in large markets on 1000 plus foot TV transmitter towers, giving them very high HAAT, and can give 250 watt translators signals approaching that of a 3 kW Class A station, or even more in some instances. And that they can interfere already with numerous former Class A frequencies and stations close by, like 40 odd miles, and limit their former de facto service areas.

But this needs to be addressed with an expanded band for AM stations to move to permanently as STATIONS, not translators with numerous capricious games being played on an unlevel playing field.


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Rich F.
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Rich F. » Sun Nov 21, 2021 8:51 am

Mike Oxlong wrote:
Sun Nov 21, 2021 7:44 am
... I'm fairly confident the FCC and CRTC are not concerned with any of the modifications we've seen in this thread so far. No one is feeding 100 watts into a collinear on top of a building or tower.
But it doesn't require such antenna gain, and/or its elevation above the Earth, and/or applied power to it to come to the attention of the FCC.

See the calculation result below, which is based on the NOUO text I quoted.

Image



bmw
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by bmw » Sun Nov 21, 2021 5:04 pm

I don't think the FCC is particularly concerned about a hobbyist, on an unused frequency, in a small town, experimenting for 10 or 15 minutes to see how far out an FM transmitter running on 2 AA batteries can get. Even optimally set up, these CCrane devices can't cover a city block with a Grade A signal.



tapeisrolling
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by tapeisrolling » Sun Nov 21, 2021 11:51 pm

I once picked up a kit for a FM transmitter at the Dayton Hamvention. A little circuit board about the size of a 9v battery. 39" wire ant. and a 9v batt. for power and it worked almost a 1/2 mile. Just plug in the headphone jack and adjust the level.
I just used it for inside a warehouse so I could listen to any station/ tape on a small FM radio since AM wouldn't penetrate.



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Turkeytop
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Re: Versatile C. Crane FM Very Low Power Transmitter

Post by Turkeytop » Wed Nov 24, 2021 10:46 pm

I have this Belkin xmtr I modified by adding about a 3 ft length of wire as an antenna. It increased the range from about 6 ft to more than 100 ft.


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