Ft. Tuthill 80 Transceiver Build

When I learned that Ari­zona QRP Club AZ ScQR­Pi­ons released a new QRP Trans­ceiv­er kit designed by N7VE (Dan Tay­loe) I placed my order with­out even think­ing twice. N7VE push­es the per­for­mance enve­lope of HF design to new lev­els (think the famous Tay­loe Detec­tor) and this lit­tle trans­ceiv­er kit is no exception.

The Ft. Tuthill 80 boasts the fol­low­ing per­for­mance and is con­sid­ered excep­tion­al regard­less of receiv­er topology:

Receiv­er

• Tun­ing range: 50 kHz seg­ment of the 80m CW band. This can be extend­ed to 80 kHz by using the oth­er half of the main tun­ing capacitor.
• Cur­rent Drain: Approx­i­mate­ly 25 ma @ 12v.
• Sup­ply volt­age range: 12 to 13.8v
• Receiv­er band­width: ~600 to 700 Hz bandwidth.
• MDS receiv­er sen­si­tiv­i­ty: ‑116 dBm in a 700 Hz bandwidth
• Third order dis­tor­tion (IP3): +25 dBm
• Block­ing Dynam­ic Range (BDR): ~100 db (lim­it­ed by the cw fil­ter response)
• RIT tun­ing range: Greater than +/- 1.5 kHz from the trans­mit fre­quen­cy (total RIT range ~ 5 kHz)
• Receiv­er Type: DC receiv­er: Both side­bands (USB/​LSB) are heard at the same time

Trans­mit­ter

• Pow­er Out­put: > 2.5w out­put at 12v
• TX har­mon­ic out­put: At full trans­mit pow­er, all out­put har­mon­ics exceed FCC spec­i­fi­ca­tions of ‑45 dBc

The BDR is around the same as a ICOM IC756 Pro III for comparison…pretty damned great, and even more so con­sid­er­ing this is a Direct Con­ver­sion receiv­er! I am real­ly excit­ed to get this thing on the air!

Here is a pic­ture of the 3.5″ by 3.5″ board stuffed with some of the ceram­ic capac­i­tors and a few diodes.

The instruc­tions are clear­ly writ­ten with plen­ty of illus­tra­tions. I have devi­at­ed some­what from the instruc­tions how­ev­er, as I did not have a device to match .1μF capac­i­tors for the fil­ter sec­tion. The match­ing is option­al, but I fig­ured with such a fine per­form­ing receiv­er I had bet­ter do it cor­rect­ly. Both my old Fluke and even old­er Radio Chalet mul­ti-meters are sans capac­i­tance mea­sure­ment, so I placed an order for the sexy LC meter from AADE–I have had my eye on that device for a long time and now it fit into my evil plans.

I skipped ahead and would the three toroidal trans­form­ers and two toroidal induc­tors. I find wind­ing toroids is only semi-tedious and only dif­fi­cult the cou­ple times when I lost focus/​turns count. I also pre­pared the final tran­sis­tors and heat-sink as instruct­ed. I am like­ly to delay mount­ing the trim­mers and inte­grat­ed cir­cuits until I match and install the .1μF caps in order to leave enough work­ing room. The man­u­al states about a 6 hour build time; I will be tak­ing mine in stages.

I will post pic­tures of my progress as I stuff the board.