THP FAQ

All THP amplifiers use high-speed, high current relays for QSK operation. It is appropriate to consider a few timing issues to consider when operating QSK.

Typically the THP T/R amplifier relay will engage 7-8ms after the amplifier is keyed by your transceiver, and the THP amplifier relay will drop-out typically 5-6ms after your transceiver un-keys the amplifier. Normally, most transceivers key the amplifier immediately upon keying your radio (your first “dit” or “dah”). However, it takes the transceiver some time to actually generate the RF signal – usually this is longer than the time for the THP relays to operate (which is good). The following are some typical measured and/or spec’d “amp key to RF output” delays of recent popular transceivers:

For transceivers with an adjustable delay, we recommend that you set the delay for 10ms. Remember, it takes the transceiver at least 5ms to generate RF after being keyed, so adding a little delay to this will not noticeably affect your keying unless you operate at very high CW speeds. The length of a “dit” in milliseconds can be calculated as follows:

So for 25WPM, the length of a “dit” is 48ms. Therefore, adding just a few milliseconds of delay to your amp-enable-to-RF output will not normally be noticeable. Of course, you can always adjust your CW “weighting” control if you feel this is necessary.

Finally, most transceivers also take 3-6ms for the RF to decay when you release the key, and do not un-key the amplifier until this has occurred. A few transceivers do un-key the amplifier slightly before RF has decayed to zero (IC-706/7000, TenTec OmniV, and possibly other transceivers), however the 5-6ms relay release timing of the THP amplifier relays normally ensures that even with these transceivers the RF has decayed to zero before the relays operate.

The THP HL-1.1, HL-1.2 and HL-1.5 amplifiers may be configured for operation from either 120- or 240-VAC. We recommend using 240VAC if at all possible. There are several reasons for this:

1) Most US residential house wiring uses 14-gauge solid copper wire, and is therefore limited (and fused) to 15-amps. This is very close to the current required by the HL-1.1 and HL-1.2 amplifiers at 120VAC, and is certainly below the 20-amps maximum required by the HL-1.5 amplifier.

2) While you will normally NOT blow your fuse or circuit breaker during amateur intermittent operation (even at 20-amps on a 15-amp circuit), the voltage drop in your AC circuit can be substantial. Voltage drops of as much as 20VAC have been measured on residential 15-amp circuits at 15-amps when the amplifier is located on the opposite side of the house from the breaker box.

a. This high voltage drop will result in corresponding drop in the drain voltage on the final transistors for the HL-1.2 and HL-1.5 amplifiers, resulting in lower output power and higher intermodulation products.

b. Since the HL-1.1 amplifier uses a switching power supply, there will be no change in the regulated drain voltage, however the AC input current will be increased above the normal 15-amp maximum when the AC input voltage drops, which increases the AC input voltage drop! In this amplifier, the POWER output remains constant because of the regulated switching power supply, therefore the input current MUST increase as the input AC voltage decreases.

c. It is not uncommon for there to be only one branch circuit feeding your shack. Therefore, the (typical) three-amps required by your transceiver will also add to the overall AC current required.

d. Finally, at the very least you will experience flickering of lights in your home as you key your transceiver!

You are spending several thousand dollars when you invest in an HF amplifier. Please consider spending a few hundred dollars more to have a dedicated 240VAC line run to your shack.

THP provides ALC & Amplifier Keying cables (RCA) for all amplifiers, and Band Data cables for some popular transceivers (RS232 for Kenwood, Band Data for Yaesu, and CI-V for ICOM). However, additional cabling is required for many transceivers. Examples:

1) Some transceivers don’t have standard RCA ALC and amplifier-keying interfaces. These include:

a. Kenwood transceivers: ALC and amplifier keying is provided on an accessory connector only. This is a 8-pin MiniDIN on the TS-480, and 7-Pin DIN on most other Kenwood radios.

b. Icom IC-706/7000 transceivers. Both ALC and amplifier keying outputs are only available on the 13-pin DIN accessory connector.

c. Elecraft K3 transceiver: ALC and Band Data are only available on the 15-pin HD15 Accessory connector.

2) Even if a transceiver has an RCA amp-key output, this may only be available as a relay contact. A solid-state switching output may only be available on an accessory connector. A solid-state switching output is recommended for QSK (full break-in) operation, or if you simply wish to turn off that clacking internal amplifier-keying relay in your transceiver. Examples:

a. Yaesu Field/MKV/2000 transceivers only have a solid-state amplifier keying output on the Band Data connector.

b. Icom IC-746/756 only have solid-state switching outputs on an accessory connector.

c. Kenwood radios have a solid-state output that goes to +12V for amplifier keying. This is essentially opposite the “key to ground” of most other transceivers.

Please contact Array Solutions for the specific cable you require for your THP amplifier.

Q: I have an Elecraft K3. Does the HL-1.5 and HL-2.5 track the band data output of the K3?

A: Yes, the BCD band data output of the K3 looks just like the BCD band data output of Yaesu transceivers, and so the HL-1.5 and HL-2.5 amplifiers will decode and track the band changes of the Elecraft K3. You will need a cable that connects to the K3 HD15 accessory connector to bring out the band data and ALC interfaces connections from the K3. Array Solutions makes the K3THP1 and K3THP2 cables for the HL-1.5 and HL-2.5 amplifiers, respectively. There is also a K3THP3 cable which just brings out the K3 ALC interface for the HL-1.1 and HL-1.2 amplifiers.

Early K3 transceivers had only open-drain band data outputs, and the K3 ALC input was not compatible with the standard -4VDC ALC standard. Beginning with K3 serial number around 2370 (and deliveries beginning in December 2008), the band-data outputs are now TTL compatible and the ALC input voltage range has been corrected. Elecraft has also published an official modification for both of these issues (see K3 mods at www.elecraft.com).

Incidentally, while TTL-compatible band data outputs are necessary for the HL-1.5, the open-drain band data outputs will work with the HL-2.5.

A: ALC is not absolutely necessary, but it does provide overdrive protection for the amplifier. We recommend that ALC be connected and properly adjusted (refer to the amplifier manual) if an ALC interface is available on your transceiver.

Q: Do the HL-1.5 and HL-2.5 amplifiers support band data interfacing to TenTec transceivers?

A: Currently THP does not support the RS232 serial interface for TenTec. Of all the TenTec transceivers, the Orion I/II do have a Band Data output, however this does not follow any standard protocols. Array Solutions has built an “Orion-to-THP amp” interface prototype. This is an active decoder that turns the Orion band data outputs into the standard BCD output. We’re currently evaluating whether there is enough demand to make this into a product.

A: Yes. Internal relays bypass the tuner completely when the HC-1.5KAT is off or not on-line.

Q: The HC-1.5KAT Tuner manual specifies a maximum tuning power of 80W. Can I damage the HC-1.5KAT if I accidentally use more power than this during tuning?

A: First of all, the HC-1.5KAT disables the amplifier prior to tuning, so you don’t have to worry about turning off your amplifier when tuning is necessary. In any case, the HC-1.5KAT will not be damaged with tuning power levels up to even 500 watts. However, high power tuning could be bad for your transceiver, therefore we suggest you limit your tuning power to less than the full output power capability of your transceiver.

Q: I see that THP recommends setting specific band segments when using the HC-1.5KAT on 160- and 80-meters. Why is this?

A: The HC-1.5KAT uses variable capacitors driven by stepper motors as opposed to many competitors that use fixed, relay-switched capacitors. While the variable capacitors are higher Q, higher voltage rated, and permit smooth tuning, they are limited in value. Therefore, THP provides for optimum tuning when a band segment is manually selected prior to tuning.

Q: According to the HC-1.5KAT manual, you should reduce power when the SWR is in the 3-4:1 range. Can you elaborate on this?

A: The HC-1.5KAT can operate safely at an SWR of 4:1. However, these conditions do result in high RF voltages on the feedline which can lead to possible RF burns, cable failure, and even arcing of the RF connectors. Therefore it is prudent to reduce power under high SWR conditions.

Most transceivers take 3-6ms for the RF to decay when you release the key, and do not un-key the amplifier until AFTER this has occurred. A few transceivers do un-key the amplifier BEFORE the transceiver's RF has decayed to zero, which means that you can hot-switch the amplifier when the transceiver un-keys the amplifier. These transceivers include the ICOM IC-706/7000 (RF persists 4.5-5.5ms after un-keying the amplifier), and TenTec Omni V/VI (RF persists ~10ms after un-keying the amplifier) if you use the TX OUT-TX EN output for keying instead of the relay output. There is no delay if you use the relay output of the Omni V/VI transceivers, but this relay output wasn’t really designed for QSK operation with amplifiers. Therefore, you should only operate semi-break-in CW with the IC-706/7000, and Omni V and Omni VI transceivers. The TenTec Omni VII and Orion I/II transceiver have an “External T/R Delay” menu setting which can be adjusted for optimum amplifier drop-out switching. If you wish to operate QSK CW with the Omni VII and Orion I/II, you should increase the “External T/R Delay” on these transceivers to maximum, and then back it off to the point where you can just hear band noise or signals between your morse characters.

Q: I am trying to interface my IC-703 with the HL-45B amplifier. I built up an interface cable based on information in the HL-45B manual, but as soon as I turn on the IC-703, the HL-45B is forced to 20 meters and I can’t change bands. Any ideas?

A: The IC-703 (like the IC-706 and IC-7000) has a bi-directional keying output. As such, there is 8VDC on that output when it is not grounded for keying. The HL-45B keying input apparently has some sort of internal connection (probably very high impedance) between the keying input and the band-data input on the amp. So when a positive voltage is applied to the keying input (when the amp is not being keyed), enough voltage couples to the band data circuitry on the HL-45B that it is forced to 20 meters. All you need to do is to add a diode in series with the HL-45B keying input (cathode towards the IC-703). This blocks the voltage from the IC-703 to the HL-45B, but you will still be able to properly key the HL-45B with the IC-703.

Note newer models of the 45B will include the series diode inside the amplifier. Starting June 2009.