From eBay seller "mht-broadcast" (Morris Hughes Technologies), below 👇 is full copy of the Description:
https://www.ebay.com/itm/197908275749
Mediumwave AM Broadcast Phase Locked Loop Carrier Generator Board
$45.00 Free Shipping
DESCRIPTION
Morris Hughes Technologies Mini PLL
*AM Broadcast Phase Locked Loop Unit
*Specifically designed for YOUR frequency!
*Lock range: 250-2550 kHz (100 kHz on request only)
*Filtered Range: +/- 100 kHz of design frequency, user changeable filter
*Super tiny! - 76 by 32 by 15mm - mounts anywhere!
*Designed to mount inside your AM transmitter
*Less than -1Hz to +1Hz drift at room temp
*Designed for single frequency use for your LPB or other AM transmitter
*Many other uses!
Board pictured is shown with filter bypassed and no connection wires
Fully built PC board. No SMD! Custom built on YOUR frequency.
This is a PLL, not a DDS. Covers 250 to 2,550 kHz in 10 kHz steps. Old school CMOS technology
We can custom build yours as low as 100 kHz upon request, however, the useful bandwidth will only be about 30 kHz
Has optional narrow band FM (NBFM) input for auxiliary audio, etc.
Designed to replace expensive/hard to find crystals for your AM transmitter
Works with all AM transmitters, including LPB 25C, 20, 30, 60 and 100 series
Fully filtered output/pure sine wave. Harmonics 30 dB down
Frequency drift is often less than 1 Hz at carrier
Power required: 11 to 15 VDC (28 mA typical) Reverse Emf protected
Available in 9 or 10 kHz standards
**please consult your transmitter manual for proper interfacing**
FULLY BUILT, TESTED AND ALIGNED ON YOUR REQUESTED FREQUENCY! NOT A KIT!!
Advantages of a PLL vs. a DDS:
A PLL can easily be frequency modulated where this is generally impossible with a DDS. Also, most DDS units have an LCD display with a confusing and frustrating 'one knob' menu navigation.
So if all you need is a single frequency, don't want all the extra menus and features that you will never use, and you want PLUG AND PLAY.... then our MINI PLL is what you need!
Our Mini PLL is capable of working a wide range of frequencies from well under 200 kHz (guaranteed lock at 250 kHz) up to 2,550 kHz. We can build a custom PLL for you down to 100 kHz but doing so might prevent some other higher frequencies from locking. The upper end is limited by the 8 bit divider and is only 2,295 kHz when using the 9 kHz reference.
PLEASE UNDERSTAND: This PLL, because of the output filtering, is only designed to operate within about 100 kHz of your requested frequency within AM band. Above and below will still work but will be attenuated.
For frequencies below 300-400 kHz the bandwidths become even narrower. We use a simple 3 component 'Butterworth' type output filter to provide a pure sine wave output with harmonic attenuation. This filter may easily be replaced (component values are calculated for your convenience and included for every 100 kHz section of AM band and extending from 50 to 2600 khz) and we provided a convenient 6 pin socket so you can change the filter components yourself.
IMPORTANT! WHEN YOU ORDER WE NEED TO KNOW 3 THINGS:
1- Your desired frequency.
2- Specify the 10 kHz American AM standard or 9 KHz Euro AM standard. Your desired frequency will be multiples of either 9 or 10 kHz so please make sure you give us a legitimate frequency our PLL can generate. Example (10khz) 530,540,550,
560, etc. Example (9khz) 531,540,549,558,567, etc. Note- our PLL will ONLY operate in the 9 or 10 khz mode, not both at once.
3- Specify Filtered or Unfiltered.
Filtered/unfiltered option: At customer's request we can omit the output filter which will allow the PLL to operate the entire design range of 250-2550 kHz. But the output will be square wave, rich in harmonics, making it unsuitable for use in radio transmitters.
Unfiltered units are well suited for RF nonlinear mixing applications such as in some receiver circuits. These components can easily be added later by the user from spare parts. Contact us if you bought an unfiltered PLL and need to install a filter.
YOUR MINI PLL WILL ARRIVE WITH THE CORRECT FILTER COMPONENTS FOR YOUR REQUESTED FREQUENCY.
.........................................................................................................................................................................................................................
WHAT YOU GET:
You will receive one Mini PLL Board on YOUR FREQUENCY along with extensive ENGLISH instructions on a mini CD, including board layouts, schematics, and an all-important PLL divider look-up table should you ever need to change frequencies.
WHAT YOU WILL NEED:
The only other thing you need is a super quiet low ripple DC power source. We cannot emphasize enough that the DC be clean because a noisy power source will surely frequency modulate hum onto your carrier. This noise will set up FM sidebands and cause interference.
For critical phase sensitive applications such as in all AM stereo systems, any percentage of supply hum and noise is unacceptable. We suggest using a high frequency switching supply (such as the small inexpensive Meanwell 'cage' types.) 12V battery operation is fine. The board mounting hole dia is 2.5 mm. We recommend using two 2.5 mm metric screws (diagonal) with appropriate spacers to mount the board. No mounting hardware included.
We use a three IC CMOS well known, tried and true design. Why spend your valuable time breadboarding and probably troubleshooting your own PLL when we have what you need right here?
..................................................................................................................................................................................................................................
Circuit Specifications:
VCO Lock Range: 250- 2,550 KHz in either 9 or 10 KHz steps. Max frequency is 2550 kHz @ 10 kHz and 2295 @ 9 kHz.
Max divider range: decimal 1 to 255 (8 bit) programmable divider
Lock time: less than 1 mS
Frequency Tolerance: +/- no more than 1.5 Hz drift from 30-90 degrees F after 30 min warm-up. Approx. -20 to +40 Hz reference
calibration range (at carrier.)
Max reliable operating temperature range of VCO: 15 to 110 degrees F. System may lose lock outside of this range
Phase Noise: Better than -40 Db. down depending on power supply.
Hi Z audio input included for narrow band FM use (modulates the loop error)
NBFM deviation: Approx. 4 kHz with 100 mvrms audio drive, Hi Z unbal. 50-3,500 Hz.
Operating voltage: 11 to 15 volts. 12.5V optimum. Do not operate unit outside of this range! Reverse voltage protection diode included.
Current draw: 28 mA at 12.5 V
RF output: approx. 10 mW filtered sine wave high 1K ohm impedance. Varies with filter curve.
DC block: 100V isolation capacitor included at RF output for safe interfacing.
VCO absolute maximum design freq: 3 Mhz.
IC compliment: Three CMOS 4000 family
IC sockets: Three included, 16 pin DIP
Board dimensions: 1.25 inches W by 3 inches L by 0.57 inches H. (32 x 76 x 14.5 mm)
Board mounting hole dia: 2.5 mm (distance between holes, 71 and 26.5 mm)
Four wire interfacing: Blk- gnd, Red +DC, Yel audio in (NBFM), Blu- RF out
We are a new company to Ebay and would really appreciate positive feedback. We have built over 100 of these circuits and have not had a single failure in over 10 years. Reliability and frequency tolerance is exceptional and each unit is cleaned and tested before shipping. We stand by our products 100% and guarantee performance. In the highly unlikely event of a failure or if you are not satisfied about something, please contact us first and we'll make it right. Contact us if you have any operational questions or application questions, or need help on a specific problem.
MHT Mini PLL Unit with instructions, layouts and schematic on CD
Just $ 45 with FREE SHIPPING.
We will ship overseas using US Mail postal rates.
Proudly assembled in the USA. God Bless AMERICA!
And what exactly does it mean where it says:
PLEASE UNDERSTAND: This PLL, because of the output filtering, is only designed to operate within about 100 kHz of your requested frequency within AM band. Above and below will still work but will be attenuated.