Author Archives: bryan

UHF Test repeater is online!

444.575 is now online from high up in downtown Tampa!  It requires a PL of 146.2 Hz.  P25 is supported with a NAC of 293.

Thanks to the hard work of our members we were able to bring this online over the weekend.  It is a “Proof-of-Concept” repeater designed to cover downtown Tampa and the central business district buildings.  This necessitated a lower gain antenna for solid coverage below the site and in the surrounding ground level.

The repeater consists of the following:

  • 25W Motorola Quantar
  • DB-404 Antenna
  • Mobile notch duplexer
  • DB-404 antenna
  • 3/8″ feedline (2.3 dB loss)

We plan to change out the feedline to a higher quality Heliax cable which should improve the receiver.

Below is a projected coverage area of the repeater to a HT at 5W.  We’ve had good mobile reports much further than this shows.  Please try it out and report back on our mailing list.

Test repeater 25W DB-404 2.3db feedline loss to 5W HT unity gain coverage
Projected HT coverage into the repeater


Below are some pictures of the repeater site after we got done.

Byron K4SIP and DB-404 antenna

Byron K4SIP and DB-404 antenna

DB-404 on Roof Looking down to the Port Quantar installed in rack Quantar online Sunset over Tampa Sunset to I4 Telewave 220 Antenna




We’re 501(c)3 approved

Our IRS form 1023 was approved by the IRS, however they keyed our address in wrong to their systems.  Thus we do not have a copy of the determination letter.  Further complicating this the IRS will not resend us a copy to our correct address.  They are demanding we submit a change of address form and a letter to them…

I’m submitting a form to the IRS later today and expect to have our address and a proper copy of the 501(c)3 determination letter on our disclosures page shortly.

Bryan W9CR

224.280 repeater progress

Much progress has been made on building the main 224.280 MHz repeater.

The rack mount case has been constructed and fixed to the Hamtronics modules, and the GPSDO master 10mhz clock source has been integrated with the units.  This consists of a PIC 16f88 micro-controller running code that will spit out the appropriate bits to the CPU as it goes into transmit.



The first revision of this code simply would power up, program the PLL IC and then shut down (no CPU noise).  This worked but it had the effect of running the PLL VCO at 224.280 all the time transmitting a low level (-24dBm) signal at all times.  This is enough to open the squelch of a radio about 2 blocks away.

We solved this by making the PLL move off frequency when not keyed.  When the repeater keys up, it now moves onto frequency in about 10ms and works flawlessly.


The other major issue was microphonics due to the cheap chip caps used in the VCO circuit of the hamtronics exciter.  Cheap ceramic capacitors can be piezoelectric, and vibrations will cause them to vary (very slightly) in capacitance.   A simple taping on the box will cause the frequency to swing 10-20 khz, which is unacceptable.  The suspect capacitors were changed to mica insulated units which do not have such a problem.

Between this and the potting of the VCO coil, almost all microphonics have been eliminated from the hamtronics exciter.  A stiff rapping on the enclosure now only varies the frequency a few Hz.

Hamtronics chip caps






Florida Simulcast Group is incorporated as a charitable non-profit corporation under the laws of Florida.  This is a big step in moving our group forward, as we can now legally function as a single entity.

Our incorporation documents can be found on our disclosures page, or

We’ll be applying for 501(c)3 Tax-exempt status shortly.  In the time being we are under provisional status, meaning all donations are treated as tax deductible under IRS code.