Crystals / oscillator modules

A new item programmable from 32 KHz up to 100 MHz: http://www.silabs.com/products/clocksoscillators/mems/Pages/si504.aspx

VBR from Ivan

Could a DDS VFO be the solution? I don't know, just a suggestion.
http://midnightdesignsolutions.com/dds60/
There is also a more complete Chinese made unit available on ebay for 47$
http://www.ebay.com/itm/0-55MHz-DDS-VFO-Signal-Generator-based-on-AD9850-Direct-Digital-Synthesis-HAM-/230962784333

Toothpaste and grafite can only move frequencies by a few kHz, but I will investigate the pre-programeable oscillators - thanks Ivan.

After a few more experiments I have got som success using the original 26MHz oscillators and a 5th harmonic filter using short copper rods and caps, but one NEEDS to have two resonators to get away from the fundamental.

With an extra amplifier I have managed to get +20dBm @ 130MHz and a good -60dBr for fundamental and harmonics. But it is just a bit "touchy" and not easily altered.

BR Harry - SM0VPO

Hi,
this is one of the once-programmable types I have mentioned. Its programming requires the appropriate HW and SW. It is necessary to order them with the required frequency, so that the distributor delivers them already programmed.
Shifting Xtal frequency is possible with old Xtals in a soldered metal case or a big bakelite case. The method is probably useless with SMD parts.

BR from Ivan

http://uk.farnell.com/citizen-america/csx750pbc64-000m-ub/programmable-oscillator-64mhz-smd/dp/9214879

Programmable - however, I don't know how you would do it.

If this isn't a suitable part for Harry, looks like he'll have to get one custom made. I've even searched for a 57.6MHz xtal so he could use CMOS and divide by two, but alas......

Doesn't Harry say something on the home pages (or maybe it was in a messageboard thread) that crystals can be altered by either toothpaste on a glass sheet (to make them thinner, and resonate higher), or pencil graphite to slow them down. I wonder if he could use such a technique on something close.

Don't know what else to suggest

Hi DragonForce,
some types of monolithic XCOs may have an extra pin to pull the frequency a bit using an internal varicap. Most of them have their frequency hard fixed, though.

BR from Ivan

28.332MHz osc block - can you pull the frequency a little with these things?

http://www.ebay.co.uk/itm/28-3220-MHZ-CRYSTAL-OSCILLATOR-HAM-RADIO-TRANSMITTER-RECEIVER-UNUSED-OLD-STOCK-/300890866659?pt=UK_Mobile_Phones_Communication_Oscillators_Crystals&hash=item460e7e43e3

Can you use 14.4MHz and double it somehow?

Hi Harry, one small idea: several manufacturers (e.g. Epson or Jauch) make once-programmable XCOs. They can customize them to any frequency within the range 1 MHz - 100 MHz or more. If you find a local distributor, you can get a sample within 24 hours.

VBR from Ivan

Harry

Only ones I can find at 28.8 MHz are surface mount crystals - I doubt their fundamantal frequency is at 28.8 MHz.

Google came up with this: http://www.digikey.co.uk/scripts/dksearch/dksus.dll?vendor=0&keywords=28.8MHz+crystal and no hits on a TTL oscillator block at this frequency.

May I suggest looking at any old PC motherboards or old PC add on cards - you may strike it lucky.

There are several places in China that will supply them to order, but you have to buy 10 - and I'm not sure of the cost. I could certainly try and find out for you if you want me to. Maybe you could make up and sell a kit with the other remaining 9? lol!!

I'm not a radio ham, so I don't know what a "G-station" is (unless it's a UK ham) and after a similar chat with my friend GW1XVC last year, I'm not even sure if these crystals are suitable, but these are the closest frequencies I could find...

28.738880 MHz and 28.850000 MHz HC-6 at $4-5 each at http://www.surplussales.com/Crystals/Crystals-6.html (US)

28.6363 MHz HC-18 at from a UK eBay seller www.heweb.co.uk, item 390561112342. Starting price £2.50 for 10, no bids as yet.

Site appears to be http://www.harrisonelectronics.co.uk/index.htm but no crystals listed there!

HTH,
Martin

Hi all (and that means both of you :-)

I have today been listening to a G-station on 14.175MHz on my FT290 using a home.made transverter. Unfortunately I am still using the 26MHz TTL oscillator to drive a transistor hard, then pick out the 5th harmonic. Instead of using the resonant rods as I used on my homepages http://www.sm0vpo.com:800/conv/xtal-lo-0.htm I am using a more conventional tuned circuit. It works a treat but the level is a bit low although the spectral purity is not good.

The problem I have is that if I want to have 160m and 80m bands I need an oscillator module (or fundamental crystal) for 28.8MHz. Does anyone have such a device? I can exchange 26MHz oscillator modules and share the circuit, but I will share circuits anyway via the homepages.

I hope to go to Spain in May and I want to use my FT290 (handbag portable) on 3.5 and 14MHz.

BR Harry - SM0VPO