Alfonso Faustino: Super Heterodyne vs. Direct Conversion, and Front-end Transceivers

BLUF (Bottom Line Up Front): Your transceivers should be Super Heterodyne and have front-end filters (the ability to block unwanted RF) when in ICS-based emergency operations.  If you don’t get Super Heterodyne transceivers and don’t have a filter for the front-end, you will experience desensitizing in your transceivers while involved with ICS-based emergency comm operations: RX-blank-out from other transceivers transmitting a signal nearby — within 15 feet; or, your will get inter-modulation, which means your frequency will hear hear static, or you will get transmissions from another frequency, and you will not be able to transmit.

Transceivers I used during my ICS-based emergency comm drills are Motorola and Yaesu — these transceivers are Super Heterodyne and have state-of-the-art front-end filters and other effective technologies to block out RF signals from other transceivers that are nearby.  Of course, there are other Super Heterodyne transceivers with front-end filters beside Motorola and Yaesu, such as, but not limited to, Hytera and Kenwood, but I’ve not used those brands.

Those cheap transceivers, like those oriental transceivers under $100, are usually direct conversion AND have no front-end filters, which will add to desensitizing your transceiver while you are in RX or TX mode in close quarters while in an emergency drill or training exercise.

So, what does this information look like when out in the field?

Here is a video clip of my Motorola XPR 7550e (UHF) blocking out the incoming signal of my Ailunce HD1GPS.  The Ailunce HD1GPS, regrettably, is Direct Conversion and doesn’t appear to use any front-end filtering system.  In an emergency ICS-based emergency comm environment, the proximity of different operators using their transceivers are as close to each other, as shown in my video clip.

Transceivers like the Ailunce HD1GPS are okay to use in non ICS-based emergency comms operations: social and individual emergency comms tool; however, if your social and individual emergency comms involve a group setting, meaning you are gonna be engaged in RX and TX with other operators in close proximity, within 15 feet, then you will experience desensitizing.

The best thing to do, is purchase a super heterodyne transceiver — you can use it for ICS-based emergency comm drills, group social HAM operations, and non ICS-base emergency drills with your radio club.

DICATA:

Tons of information resides on the Internet regarding front-end filters, blocking, cross modulations, intermodulation, Super Heterodyne, and Direct Conversion; hence, I’m not gonna talk about the technical physics about the way front-end, Super Heterodyne, and Direct Conversion transceivers work; rather, I’m gonna tell you about the results of using Super Heterodyne, front-end filters, and Direct Conversion transceivers in my real-live activities and experiences.

Based upon my emergency ICS-base comms crisis training and drills out in the field, consider getting a Super Heterodyne transceiver that has front-end filters, like a Motorola.  Here’s why…

I do a lot of ICS-based drill and training work out in the field with the San Francisco Police Department, San Francisco Fire Department, Sheriff’s Department, and, soon, the US Coast Guard.

My equipment must be reliable, durable, and interoperable when dealing with mutual aid ICS-based activities.

My speciality is SAR and SAF missions — land, sea, and air.  My communications equipment must be on-point (a term I use from my time with ballerinas — I have a soft-spot for ballerinas).  If my comm equipment doesn’t work during my ICS-basdd emergency comms drills and training, well, I’m unable to do my job and will let people down that depend on my communications skills to get help to those in need.

In my experiences, regarding social and ICS-based communications, nothing beats Motorola transceivers — they have years and years of effective research, design, and development put into their hand-held and mobile transceivers.  They are reliable and durable, and provide me with crystal clear communications over the radio frequencies.

I was doing an ICS-based emergency comms drill this past weekend with the San Francisco Fire Department; and, many people on the comms team had those oriental transceivers.  I, of course, had my Motorola XPR 7550 (VHF), which operated without a single glitch — no surprise and par for the course when using Motorola.

Whenever there is a disaster drill, other comm devices will be in use; and, the radio waves will be busy in the immediate areas: TX and RX will be abundant.

The abundance of RX and TX will be challenging for any comms operator to get their message across the table of those that need the message — in this case, the Battalions of SFFD located in Mobile Command 1.

Last weekend, ACS changed up one of our Battalion’s frequency to 146.xxx.  I was the comms contact and lead to the Battalion (AKA: Battalion’s Comm Operator: BCO); and, near me, within 15 feet was a tactical team (ETAC) getting information from a team out in the field.  When ETAC transmitted to the field, BCOs using those cheap oriental transceivers experienced two events:

  1. They could not hear any receiving messages from their teams in the field nor SFFD’s Mobile Command 1.  So, if SFFD’s Mobile Command 1 was sending out a transmission to a BCO, and he was using a cheap oriental transceiver that has direct conversion and no front-end filter, that BCO would not hear SFFD’s Mobile Command 1’s message — the BCO would just hear dead air or static; and or,
  2. The BCO would hear the transmission of ETAC that was within 15 feet of him operating on a different frequency.  So, if ETAC was operating on 145.xxx and the BCO was operating on 146.xxx, BCO would lose communications with SFFD’s Mobile Command 1, and BCO would hear the transmission of ETAC using an entirely different frequency — inter-modulation.

Here is a video clip of my Motorola XPR 7550e (UHF) blocking out the incoming signal of my Ailunce HD1GPS.  The Ailunce HD1GPS, regrettably, is Direct Conversion and doesn’t appear to use any front-end filtering system.  In an emergency ICS-based comm environment, the proximity of different operators using their transceivers are as close to each other as shown in my video clip.

So, what caused these two events?

Well, the BCOs were using cheap oriental transceiver that were direct conversion without front-end filters.  Direct conversion transceivers without front-end filters are primarily found in cheap oriental transceivers — you know the brands that fall in this category.

Upper-end transceivers, like my Motorola XPR 7550, use Super Heterodyne technology with effective state-of-the-art filters and technologies that prevent inter-modulation and frequency interferences from other transceiver transmitting nearby.

I use Motorola because, I cannot afford to have my communication interrupted or impeded by other frequencies near me.  When I’m talking to SFFD’s Mobile Command 1, as a BCO, I must convey my emergency messages to SFFD’s Mobile Command 1 to get help without interference — injured civilians depend on me getting my messages out to SFFD’s Mobile Command 1; and, conversely, SFFD’s Mobile Command 1 needs to reach me in order to get assistance from me for their first responders out in the danger zone.

I said it before, and I will say it again…”Invest, one time, in a medium to high-end transceiver — don’t buy cheap oriental stuff — they are junk in emergency operations.”

These are the brands I recommend you to purchase:

  • Motorola
  • Yaesu

Of course, my list is not a complete list, but I’ve used these models, and they use the  Super Heterodyne technology.

Also, during last week’s drill with SFFD, one of the ETACs asked me to help him “tune” his transceiver; because, the voice of the incoming operator was faint — the static overwhelmed the voice of the incoming operator.

I didn’t want to hurt his feelings — my inner voice was saying, “Dude, you’re out of luck — you’ve got a cheap piece of shit oriental transceiver, and there is nothing I can do about the static — that thing hasn’t a front end filter; and, if it did, it’s crap.

What did he expect to get with a $40 or $60 oriental transceiver?

By the way, we were using simplex, and SFFD’s Mobile Command 1 was about 1.5 – 2 blocks aways from our staging area — there is no reason that ETAC guy should be hearing any static from SFFD Mobile Command 1.

Now, if you’re just gonna shoot-the-shit with another operator in a social settings; or, if you want a transceiver for your bug-out and EDC pack, then it really doesn’t matter having Super Heterodyne nor having front-end filters — a cheap oriental transceiver will do the job; because, most likely, you ain’t gonna be within 15 feet of another HAM operator. Most of the time, in a social HAM conversations and your own emergency experiences, you will not be near another HAM operator; so, you won’t experience inter-modulation nor RX blank-outs as a result of having a direct conversion transceiver without front-end filters.

For social HAM conversations on analog and DMR, I recommend the Ailunce HD1 or the Ailunce HD1GPS model. This is a good transceiver for social conversations on analog and DMR; and, it is a good individual emergency comms transceiver, as long as you are not within 15 feet of another HAM operator.

If you want to have social HAM conversations on analog and System Fusion’s WiresX, then I recommend the Yaesu.

The nice thing about Yaesu is they have good front-end filters and they are all Super Heterodyne — so, they satisfy my ICS-based emergency comms requirements.

Because Yaesu uses Super Heterodyne and have front-end filtering in their transceivers, I use the Yaesu FT1XDR as a back-up to my Motorola XPR 7550e (UHF), Motorola XPR 7550 (VHF), and my Motorola XPR 7580 (UHF 800 & 900 MHz) when I’m active in my emergency training and drills with the San Francisco Police Department, San Francisco Fire Department, Sheriff’s Department, and soon-to-be US Coast Guard.

Unfortunately, I won’t use the Ailunce HD1GPS when I’m active in my ICS-based emergency training and drills with the San Francisco Police Department, San Francisco Fire Department, Sheriff’s Department, and soon-to-be US Coast Guard; because, the HD1GPS is direct conversion and they don’t have a good front-end filter or software to prevent desensitizing during my ICS-based emergency comms drill and training — Ailunce told me they are correcting this problem. I hope they will; because, I really dig the Ailunce HD1GPS transceiver; and, I would like to use it as a back-up to my Motorolas during my ICS-based emergency drills and training.

Now, when you research Super Heterodyne vs Direct Conversion, like anything else, you will read about the positives and negatives of both. You will also find out the importance of the front-end filters and software in the transceiver to help filter out inter-modulation when using Super Heterodyne or Direct Conversion.

After researching all this information, I had to make a choice…with the help of my mentor, I went with Motorola: Super Heterodyne and state-of-the-art front-end filtering with software to help eliminate desensitizing and intermodulation.

If you don’t have a mentor to guide you, then read about the industry leaders, Motorola, Kenwood, Hytera, and Yaesu are using, and make your decision from that point of reference.

Check 6!

/s/ Alfonso Faustino (K6ASF)

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